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 $62.85   9.362%   $68.734   $68.73   $68.75   $68.70  
  Purchase #2 $151.66   10.291%   $167.2673   $167.27   $167.25   $167.30  
  Purchase #3 $16.98   3.606%   $17.5923   $17.59   $17.60   $17.60  
  Purchase #4 $43.45   10.104%   $47.8402   $47.84   $47.85   $47.80  
  Purchase #5 $24.42   5.570%   $25.7802   $25.78   $25.80   $25.80  
  Purchase #6 $232.35   12.310%   $260.9523   $260.95   $260.95   $261.00  
  Purchase #7 $193.48   8.840%   $210.5836   $210.58   $210.60   $210.60  
  7 purchase totals = $725.19       $798.7499   $798.74   $798.80   $798.80