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 $40.81   13.216%   $46.2034   $46.20   $46.20   $46.20  
  Purchase #2 $236.57   4.282%   $246.6999   $246.70   $246.70   $246.70  
  Purchase #3 $158.43   10.757%   $175.4723   $175.47   $175.45   $175.50  
  Purchase #4 $212.27   12.350%   $238.4853   $238.49   $238.50   $238.50  
  Purchase #5 $182.88   11.342%   $203.6222   $203.62   $203.60   $203.60  
  Purchase #6 $177.98   13.710%   $202.3811   $202.38   $202.40   $202.40  
  Purchase #7 $126.86   4.383%   $132.4203   $132.42   $132.40   $132.40  
  7 purchase totals = $1,135.80       $1,245.2845   $1,245.28   $1,245.25   $1,245.30