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 $59.85   4.618%   $62.6139   $62.61   $62.60   $62.60  
  Purchase #2 $178.41   9.781%   $195.8603   $195.86   $195.85   $195.90  
  Purchase #3 $46.48   12.253%   $52.1752   $52.18   $52.20   $52.20  
  Purchase #4 $144.35   6.812%   $154.1831   $154.18   $154.20   $154.20  
  Purchase #5 $236.63   6.320%   $251.585   $251.59   $251.60   $251.60  
  Purchase #6 $76.37   9.534%   $83.6511   $83.65   $83.65   $83.70  
  Purchase #7 $146.53   10.481%   $161.8878   $161.89   $161.90   $161.90  
  7 purchase totals = $888.62       $961.9564   $961.96   $962.00   $962.10