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 $59.82   5.138%   $62.8936   $62.89   $62.90   $62.90  
  Purchase #2 $111.86   5.662%   $118.1935   $118.19   $118.20   $118.20  
  Purchase #3 $211.43   9.506%   $231.5285   $231.53   $231.55   $231.50  
  Purchase #4 $239.50   9.563%   $262.4034   $262.40   $262.40   $262.40  
  Purchase #5 $231.89   3.456%   $239.9041   $239.90   $239.90   $239.90  
  Purchase #6 $67.46   8.474%   $73.1766   $73.18   $73.20   $73.20  
  Purchase #7 $42.33   11.207%   $47.0739   $47.07   $47.05   $47.10  
  7 purchase totals = $964.29       $1,035.1736   $1,035.16   $1,035.20   $1,035.20