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 $56.52   10.791%   $62.6191   $62.62   $62.60   $62.60  
  Purchase #2 $222.61   3.328%   $230.0185   $230.02   $230.00   $230.00  
  Purchase #3 $33.47   4.214%   $34.8804   $34.88   $34.90   $34.90  
  Purchase #4 $146.94   8.375%   $159.2462   $159.25   $159.25   $159.20  
  Purchase #5 $37.47   12.416%   $42.1223   $42.12   $42.10   $42.10  
  Purchase #6 $183.91   5.634%   $194.2715   $194.27   $194.25   $194.30  
  Purchase #7 $180.34   13.147%   $204.0493   $204.05   $204.05   $204.00  
  7 purchase totals = $861.26       $927.2073   $927.21   $927.15   $927.10