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 $104.76   10.367%   $115.6205   $115.62   $115.60   $115.60  
  Purchase #2 $234.74   11.817%   $262.4792   $262.48   $262.50   $262.50  
  Purchase #3 $157.48   4.608%   $164.7367   $164.74   $164.75   $164.70  
  Purchase #4 $172.54   8.583%   $187.3491   $187.35   $187.35   $187.30  
  Purchase #5 $29.43   12.140%   $33.0028   $33.00   $33.00   $33.00  
  Purchase #6 $204.95   9.447%   $224.3116   $224.31   $224.30   $224.30  
  Purchase #7 $218.45   13.411%   $247.7463   $247.75   $247.75   $247.70  
  7 purchase totals = $1,122.35       $1,235.2462   $1,235.25   $1,235.25   $1,235.10