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 $182.57   7.133%   $195.5927   $195.59   $195.60   $195.60  
  Purchase #2 $6.57   9.327%   $7.1828   $7.18   $7.20   $7.20  
  Purchase #3 $47.38   7.535%   $50.9501   $50.95   $50.95   $51.00  
  Purchase #4 $36.75   9.272%   $40.1575   $40.16   $40.15   $40.20  
  Purchase #5 $127.62   6.865%   $136.3811   $136.38   $136.40   $136.40  
  Purchase #6 $64.85   12.512%   $72.964   $72.96   $72.95   $73.00  
  Purchase #7 $21.81   11.644%   $24.3496   $24.35   $24.35   $24.30  
  7 purchase totals = $487.55       $527.5778   $527.57   $527.60   $527.70