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 $54.75   13.264%   $62.012   $62.01   $62.00   $62.00  
  Purchase #2 $109.54   13.231%   $124.0332   $124.03   $124.05   $124.00  
  Purchase #3 $52.77   8.550%   $57.2818   $57.28   $57.30   $57.30  
  Purchase #4 $64.46   6.104%   $68.3946   $68.39   $68.40   $68.40  
  Purchase #5 $227.79   7.597%   $245.0952   $245.10   $245.10   $245.10  
  Purchase #6 $102.42   13.607%   $116.3563   $116.36   $116.35   $116.40  
  Purchase #7 $55.78   8.484%   $60.5124   $60.51   $60.50   $60.50  
  7 purchase totals = $667.51       $733.6855   $733.68   $733.70   $733.70