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 $60.85   4.763%   $63.7483   $63.75   $63.75   $63.70  
  Purchase #2 $176.50   10.665%   $195.3237   $195.32   $195.30   $195.30  
  Purchase #3 $58.53   11.167%   $65.066   $65.07   $65.05   $65.10  
  Purchase #4 $45.98   4.196%   $47.9093   $47.91   $47.90   $47.90  
  Purchase #5 $182.66   12.844%   $206.1209   $206.12   $206.10   $206.10  
  Purchase #6 $156.85   11.551%   $174.9677   $174.97   $174.95   $175.00  
  Purchase #7 $16.58   13.591%   $18.8334   $18.83   $18.85   $18.80  
  7 purchase totals = $697.95       $771.9693   $771.97   $771.90   $771.90