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 $229.84   7.472%   $247.0136   $247.01   $247.00   $247.00  
  Purchase #2 $59.65   5.138%   $62.7148   $62.71   $62.70   $62.70  
  Purchase #3 $158.87   7.487%   $170.7646   $170.76   $170.75   $170.80  
  Purchase #4 $16.74   5.672%   $17.6895   $17.69   $17.70   $17.70  
  Purchase #5 $50.29   4.533%   $52.5696   $52.57   $52.55   $52.60  
  Purchase #6 $86.95   8.597%   $94.4251   $94.43   $94.45   $94.40  
  Purchase #7 $161.75   11.657%   $180.6052   $180.61   $180.60   $180.60  
  7 purchase totals = $764.09       $825.7824   $825.78   $825.75   $825.80