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 $246.38   11.514%   $274.7482   $274.75   $274.75   $274.70  
  Purchase #2 $134.85   5.859%   $142.7509   $142.75   $142.75   $142.80  
  Purchase #3 $229.90   6.803%   $245.5401   $245.54   $245.55   $245.50  
  Purchase #4 $156.36   8.572%   $169.7632   $169.76   $169.75   $169.80  
  Purchase #5 $195.82   11.745%   $218.8191   $218.82   $218.80   $218.80  
  Purchase #6 $230.77   12.304%   $259.1639   $259.16   $259.15   $259.20  
  Purchase #7 $151.44   4.236%   $157.855   $157.86   $157.85   $157.90  
  7 purchase totals = $1,345.52       $1,468.6404   $1,468.64   $1,468.60   $1,468.70