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 $195.48   4.327%   $203.9384   $203.94   $203.95   $203.90  
  Purchase #2 $152.50   8.435%   $165.3634   $165.36   $165.35   $165.40  
  Purchase #3 $180.72   7.689%   $194.6156   $194.62   $194.60   $194.60  
  Purchase #4 $61.43   7.843%   $66.248   $66.25   $66.25   $66.20  
  Purchase #5 $233.90   11.188%   $260.0687   $260.07   $260.05   $260.10  
  Purchase #6 $155.82   7.421%   $167.3834   $167.38   $167.40   $167.40  
  Purchase #7 $129.86   6.220%   $137.9373   $137.94   $137.95   $137.90  
  7 purchase totals = $1,109.71       $1,195.5548   $1,195.56   $1,195.55   $1,195.50