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 $68.43   8.434%   $74.2014   $74.20   $74.20   $74.20  
  Purchase #2 $195.67   9.787%   $214.8202   $214.82   $214.80   $214.80  
  Purchase #3 $58.42   7.445%   $62.7694   $62.77   $62.75   $62.80  
  Purchase #4 $96.78   7.433%   $103.9737   $103.97   $103.95   $104.00  
  Purchase #5 $7.78   8.451%   $8.4375   $8.44   $8.45   $8.40  
  Purchase #6 $198.98   7.427%   $213.7582   $213.76   $213.75   $213.80  
  Purchase #7 $211.50   5.715%   $223.5872   $223.59   $223.60   $223.60  
  7 purchase totals = $837.56       $901.5476   $901.55   $901.50   $901.60