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 $146.50   3.391%   $151.4678   $151.47   $151.45   $151.50  
  Purchase #2 $183.71   10.861%   $203.6627   $203.66   $203.65   $203.70  
  Purchase #3 $222.95   4.145%   $232.1913   $232.19   $232.20   $232.20  
  Purchase #4 $45.54   4.266%   $47.4827   $47.48   $47.50   $47.50  
  Purchase #5 $48.95   4.456%   $51.1312   $51.13   $51.15   $51.10  
  Purchase #6 $62.56   11.277%   $69.6149   $69.61   $69.60   $69.60  
  Purchase #7 $167.91   11.708%   $187.5689   $187.57   $187.55   $187.60  
  7 purchase totals = $878.12       $943.1195   $943.11   $943.10   $943.20