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 $219.91   5.510%   $232.027   $232.03   $232.05   $232.00  
  Purchase #2 $13.84   5.554%   $14.6087   $14.61   $14.60   $14.60  
  Purchase #3 $166.49   4.664%   $174.2551   $174.26   $174.25   $174.30  
  Purchase #4 $174.68   13.841%   $198.8575   $198.86   $198.85   $198.90  
  Purchase #5 $229.76   11.507%   $256.1985   $256.20   $256.20   $256.20  
  Purchase #6 $79.75   10.534%   $88.1509   $88.15   $88.15   $88.20  
  Purchase #7 $93.38   13.320%   $105.8182   $105.82   $105.80   $105.80  
  7 purchase totals = $977.81       $1,069.9159   $1,069.93   $1,069.90   $1,070.00