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 $61.75   8.499%   $66.9981   $67.00   $67.00   $67.00  
  Purchase #2 $54.92   13.398%   $62.2782   $62.28   $62.30   $62.30  
  Purchase #3 $200.93   8.232%   $217.4706   $217.47   $217.45   $217.50  
  Purchase #4 $182.98   10.466%   $202.1307   $202.13   $202.15   $202.10  
  Purchase #5 $173.44   11.264%   $192.9763   $192.98   $193.00   $193.00  
  Purchase #6 $97.48   11.462%   $108.6532   $108.65   $108.65   $108.70  
  Purchase #7 $51.39   6.546%   $54.754   $54.75   $54.75   $54.80  
  7 purchase totals = $822.89       $905.2611   $905.26   $905.30   $905.40