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 $60.33   3.725%   $62.5773   $62.58   $62.60   $62.60  
  Purchase #2 $51.38   3.787%   $53.3258   $53.33   $53.35   $53.30  
  Purchase #3 $216.58   9.139%   $236.3732   $236.37   $236.35   $236.40  
  Purchase #4 $122.80   8.175%   $132.8389   $132.84   $132.85   $132.80  
  Purchase #5 $135.74   4.580%   $141.9569   $141.96   $141.95   $142.00  
  Purchase #6 $68.78   3.570%   $71.2354   $71.24   $71.25   $71.20  
  Purchase #7 $58.83   13.771%   $66.9315   $66.93   $66.95   $66.90  
  7 purchase totals = $714.44       $765.2390   $765.25   $765.30   $765.20