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 $57.50   9.480%   $62.951   $62.95   $62.95   $63.00  
  Purchase #2 $117.39   8.502%   $127.3705   $127.37   $127.35   $127.40  
  Purchase #3 $111.86   5.801%   $118.349   $118.35   $118.35   $118.30  
  Purchase #4 $151.36   11.781%   $169.1917   $169.19   $169.20   $169.20  
  Purchase #5 $186.78   9.697%   $204.8921   $204.89   $204.90   $204.90  
  Purchase #6 $14.85   12.516%   $16.7086   $16.71   $16.70   $16.70  
  Purchase #7 $14.86   13.192%   $16.8203   $16.82   $16.80   $16.80  
  7 purchase totals = $654.60       $716.2832   $716.28   $716.25   $716.30