Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $241.48   12.625%   $271.9669   $271.97   $271.95   $272.00  
  Purchase #2 $229.43   10.796%   $254.1993   $254.20   $254.20   $254.20  
  Purchase #3 $142.27   10.724%   $157.527   $157.53   $157.55   $157.50  
  Purchase #4 $236.99   11.214%   $263.5661   $263.57   $263.55   $263.60  
  Purchase #5 $131.41   10.813%   $145.6194   $145.62   $145.60   $145.60  
  Purchase #6 $146.35   12.385%   $164.4754   $164.48   $164.50   $164.50  
  Purchase #7 $238.76   11.191%   $265.4796   $265.48   $265.50   $265.50  
  7 purchase totals = $1,366.69       $1,522.8337   $1,522.85   $1,522.85   $1,522.90