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 $67.30   13.227%   $76.2018   $76.20   $76.20   $76.20  
  Purchase #2 $40.59   8.779%   $44.1534   $44.15   $44.15   $44.20  
  Purchase #3 $215.90   9.714%   $236.8725   $236.87   $236.85   $236.90  
  Purchase #4 $98.41   5.279%   $103.6051   $103.61   $103.60   $103.60  
  Purchase #5 $119.76   5.246%   $126.0426   $126.04   $126.05   $126.00  
  Purchase #6 $171.85   13.375%   $194.8349   $194.83   $194.85   $194.80  
  Purchase #7 $171.25   4.324%   $178.6549   $178.65   $178.65   $178.70  
  7 purchase totals = $885.06       $960.3652   $960.35   $960.35   $960.40