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 $185.26   10.440%   $204.6011   $204.60   $204.60   $204.60  
  Purchase #2 $215.40   7.410%   $231.3611   $231.36   $231.35   $231.40  
  Purchase #3 $58.68   5.733%   $62.0441   $62.04   $62.05   $62.00  
  Purchase #4 $68.38   12.821%   $77.147   $77.15   $77.15   $77.10  
  Purchase #5 $91.53   3.272%   $94.5249   $94.52   $94.50   $94.50  
  Purchase #6 $148.91   8.797%   $162.0096   $162.01   $162.00   $162.00  
  Purchase #7 $49.71   10.788%   $55.0727   $55.07   $55.05   $55.10  
  7 purchase totals = $817.87       $886.7605   $886.75   $886.70   $886.70