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 $59.45   4.278%   $61.9933   $61.99   $62.00   $62.00  
  Purchase #2 $24.53   4.303%   $25.5855   $25.59   $25.60   $25.60  
  Purchase #3 $94.97   9.436%   $103.9314   $103.93   $103.95   $103.90  
  Purchase #4 $135.26   5.406%   $142.5722   $142.57   $142.55   $142.60  
  Purchase #5 $105.74   6.359%   $112.464   $112.46   $112.45   $112.50  
  Purchase #6 $66.57   3.623%   $68.9818   $68.98   $69.00   $69.00  
  Purchase #7 $241.44   5.802%   $255.4483   $255.45   $255.45   $255.40  
  7 purchase totals = $727.96       $770.9765   $770.97   $771.00   $771.00