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 $59.28   7.503%   $63.7278   $63.73   $63.75   $63.70  
  Purchase #2 $75.50   8.500%   $81.9175   $81.92   $81.90   $81.90  
  Purchase #3 $157.80   12.242%   $177.1179   $177.12   $177.10   $177.10  
  Purchase #4 $205.26   4.752%   $215.014   $215.01   $215.00   $215.00  
  Purchase #5 $224.57   3.541%   $232.522   $232.52   $232.50   $232.50  
  Purchase #6 $23.35   4.287%   $24.351   $24.35   $24.35   $24.40  
  Purchase #7 $231.41   13.299%   $262.1852   $262.19   $262.20   $262.20  
  7 purchase totals = $977.17       $1,056.8354   $1,056.84   $1,056.80   $1,056.80