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 $62.28   9.625%   $68.2745   $68.27   $68.25   $68.30  
  Purchase #2 $146.78   4.730%   $153.7227   $153.72   $153.70   $153.70  
  Purchase #3 $229.43   6.335%   $243.9644   $243.96   $243.95   $244.00  
  Purchase #4 $194.38   7.736%   $209.4172   $209.42   $209.40   $209.40  
  Purchase #5 $217.60   6.248%   $231.1956   $231.20   $231.20   $231.20  
  Purchase #6 $243.36   3.303%   $251.3982   $251.40   $251.40   $251.40  
  Purchase #7 $44.75   4.147%   $46.6058   $46.61   $46.60   $46.60  
  7 purchase totals = $1,138.58       $1,204.5784   $1,204.58   $1,204.50   $1,204.60