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 $56.69   5.130%   $59.5982   $59.60   $59.60   $59.60  
  Purchase #2 $235.61   12.575%   $265.238   $265.24   $265.25   $265.20  
  Purchase #3 $10.70   4.553%   $11.1872   $11.19   $11.20   $11.20  
  Purchase #4 $174.28   11.682%   $194.6394   $194.64   $194.65   $194.60  
  Purchase #5 $81.33   8.160%   $87.9665   $87.97   $87.95   $88.00  
  Purchase #6 $152.49   13.744%   $173.4482   $173.45   $173.45   $173.40  
  Purchase #7 $86.30   7.128%   $92.4515   $92.45   $92.45   $92.50  
  7 purchase totals = $797.40       $884.5290   $884.54   $884.55   $884.50