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 $117.27   5.702%   $123.9567   $123.96   $123.95   $124.00  
  Purchase #2 $60.58   10.194%   $66.7555   $66.76   $66.75   $66.80  
  Purchase #3 $88.98   5.548%   $93.9166   $93.92   $93.90   $93.90  
  Purchase #4 $117.95   10.171%   $129.9467   $129.95   $129.95   $129.90  
  Purchase #5 $82.56   3.597%   $85.5297   $85.53   $85.55   $85.50  
  Purchase #6 $159.80   8.517%   $173.4102   $173.41   $173.40   $173.40  
  Purchase #7 $71.97   8.339%   $77.9716   $77.97   $77.95   $78.00  
  7 purchase totals = $699.11       $751.4870   $751.50   $751.45   $751.50