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 $43.61   5.665%   $46.0805   $46.08   $46.10   $46.10  
  Purchase #2 $167.76   3.675%   $173.9252   $173.93   $173.95   $173.90  
  Purchase #3 $107.61   4.539%   $112.4944   $112.49   $112.50   $112.50  
  Purchase #4 $85.44   10.353%   $94.2856   $94.29   $94.30   $94.30  
  Purchase #5 $145.78   5.211%   $153.3766   $153.38   $153.40   $153.40  
  Purchase #6 $46.25   3.213%   $47.736   $47.74   $47.75   $47.70  
  Purchase #7 $130.55   10.543%   $144.3139   $144.31   $144.30   $144.30  
  7 purchase totals = $727.00       $772.2122   $772.22   $772.30   $772.20