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 $94.86   3.229%   $97.923   $97.92   $97.90   $97.90  
  Purchase #2 $211.53   12.310%   $237.5693   $237.57   $237.55   $237.60  
  Purchase #3 $98.88   12.449%   $111.1896   $111.19   $111.20   $111.20  
  Purchase #4 $95.54   12.428%   $107.4137   $107.41   $107.40   $107.40  
  Purchase #5 $44.55   3.164%   $45.9596   $45.96   $45.95   $46.00  
  Purchase #6 $185.64   8.191%   $200.8458   $200.85   $200.85   $200.80  
  Purchase #7 $140.80   7.308%   $151.0897   $151.09   $151.10   $151.10  
  7 purchase totals = $871.80       $951.9907   $951.99   $951.95   $952.00