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 $64.87   10.574%   $71.7294   $71.73   $71.75   $71.70  
  Purchase #2 $201.51   6.490%   $214.588   $214.59   $214.60   $214.60  
  Purchase #3 $169.86   7.105%   $181.9286   $181.93   $181.95   $181.90  
  Purchase #4 $6.47   6.554%   $6.894   $6.89   $6.90   $6.90  
  Purchase #5 $11.91   3.273%   $12.2998   $12.30   $12.30   $12.30  
  Purchase #6 $154.52   7.324%   $165.837   $165.84   $165.85   $165.80  
  Purchase #7 $135.92   3.356%   $140.4815   $140.48   $140.50   $140.50  
  7 purchase totals = $745.06       $793.7583   $793.76   $793.85   $793.70