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 $175.75   11.116%   $195.2864   $195.29   $195.30   $195.30  
  Purchase #2 $146.26   4.378%   $152.6633   $152.66   $152.65   $152.70  
  Purchase #3 $180.86   3.136%   $186.5318   $186.53   $186.55   $186.50  
  Purchase #4 $154.79   10.456%   $170.9748   $170.97   $170.95   $171.00  
  Purchase #5 $97.98   6.251%   $104.1047   $104.10   $104.10   $104.10  
  Purchase #6 $165.63   11.763%   $185.1131   $185.11   $185.10   $185.10  
  Purchase #7 $62.55   7.677%   $67.352   $67.35   $67.35   $67.40  
  7 purchase totals = $983.82       $1,062.0261   $1,062.01   $1,062.00   $1,062.10