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 $58.61   5.756%   $61.9836   $61.98   $62.00   $62.00  
  Purchase #2 $76.68   10.594%   $84.8035   $84.80   $84.80   $84.80  
  Purchase #3 $87.44   7.842%   $94.297   $94.30   $94.30   $94.30  
  Purchase #4 $74.99   10.318%   $82.7275   $82.73   $82.75   $82.70  
  Purchase #5 $136.63   13.391%   $154.9261   $154.93   $154.95   $154.90  
  Purchase #6 $151.84   3.128%   $156.5896   $156.59   $156.60   $156.60  
  Purchase #7 $242.97   9.300%   $265.5662   $265.57   $265.55   $265.60  
  7 purchase totals = $829.16       $900.8935   $900.90   $900.95   $900.90