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 $187.27   4.109%   $194.9649   $194.96   $194.95   $195.00  
  Purchase #2 $69.90   4.330%   $72.9267   $72.93   $72.95   $72.90  
  Purchase #3 $173.62   11.415%   $193.4387   $193.44   $193.45   $193.40  
  Purchase #4 $38.49   4.633%   $40.2732   $40.27   $40.25   $40.30  
  Purchase #5 $217.76   5.258%   $229.2098   $229.21   $229.20   $229.20  
  Purchase #6 $119.53   10.796%   $132.4345   $132.43   $132.45   $132.40  
  Purchase #7 $89.28   4.463%   $93.2646   $93.26   $93.25   $93.30  
  7 purchase totals = $895.85       $956.5124   $956.50   $956.50   $956.50