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 $80.76   5.499%   $85.201   $85.20   $85.20   $85.20  
  Purchase #2 $130.49   4.505%   $136.3686   $136.37   $136.35   $136.40  
  Purchase #3 $10.88   13.754%   $12.3764   $12.38   $12.40   $12.40  
  Purchase #4 $62.55   6.327%   $66.5075   $66.51   $66.50   $66.50  
  Purchase #5 $185.26   5.808%   $196.0199   $196.02   $196.00   $196.00  
  Purchase #6 $194.85   6.748%   $207.9985   $208.00   $208.00   $208.00  
  Purchase #7 $150.82   7.304%   $161.8359   $161.84   $161.85   $161.80  
  7 purchase totals = $815.61       $866.3078   $866.32   $866.30   $866.30