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 $42.57   13.401%   $48.2748   $48.27   $48.25   $48.30  
  Purchase #2 $214.45   6.134%   $227.6044   $227.60   $227.60   $227.60  
  Purchase #3 $87.38   6.184%   $92.7836   $92.78   $92.80   $92.80  
  Purchase #4 $195.96   9.698%   $214.9642   $214.96   $214.95   $215.00  
  Purchase #5 $165.31   7.787%   $178.1827   $178.18   $178.20   $178.20  
  Purchase #6 $94.58   6.755%   $100.9689   $100.97   $100.95   $101.00  
  Purchase #7 $230.89   9.658%   $253.1894   $253.19   $253.20   $253.20  
  7 purchase totals = $1,031.14       $1,115.9680   $1,115.95   $1,115.95   $1,116.10