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 $112.60   5.471%   $118.7603   $118.76   $118.75   $118.80  
  Purchase #2 $217.43   10.351%   $239.9362   $239.94   $239.95   $239.90  
  Purchase #3 $61.34   11.267%   $68.2512   $68.25   $68.25   $68.30  
  Purchase #4 $247.69   10.775%   $274.3786   $274.38   $274.40   $274.40  
  Purchase #5 $239.95   9.872%   $263.6379   $263.64   $263.65   $263.60  
  Purchase #6 $8.99   4.367%   $9.3826   $9.38   $9.40   $9.40  
  Purchase #7 $242.31   7.408%   $260.2603   $260.26   $260.25   $260.30  
  7 purchase totals = $1,130.31       $1,234.6071   $1,234.61   $1,234.65   $1,234.70