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 $91.42   4.574%   $95.6016   $95.60   $95.60   $95.60  
  Purchase #2 $211.70   11.835%   $236.7547   $236.75   $236.75   $236.80  
  Purchase #3 $188.44   11.402%   $209.9259   $209.93   $209.95   $209.90  
  Purchase #4 $24.76   5.712%   $26.1743   $26.17   $26.15   $26.20  
  Purchase #5 $225.62   13.172%   $255.3387   $255.34   $255.35   $255.30  
  Purchase #6 $212.95   10.230%   $234.7348   $234.73   $234.75   $234.70  
  Purchase #7 $188.34   11.764%   $210.4963   $210.50   $210.50   $210.50  
  7 purchase totals = $1,143.23       $1,269.0263   $1,269.02   $1,269.05   $1,269.00