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 $10.95   7.320%   $11.7515   $11.75   $11.75   $11.80  
  Purchase #2 $182.26   6.692%   $194.4568   $194.46   $194.45   $194.50  
  Purchase #3 $239.76   6.345%   $254.9728   $254.97   $254.95   $255.00  
  Purchase #4 $247.98   13.859%   $282.3475   $282.35   $282.35   $282.30  
  Purchase #5 $237.27   8.763%   $258.062   $258.06   $258.05   $258.10  
  Purchase #6 $249.92   7.116%   $267.7043   $267.70   $267.70   $267.70  
  Purchase #7 $42.41   5.461%   $44.726   $44.73   $44.75   $44.70  
  7 purchase totals = $1,210.55       $1,314.0209   $1,314.02   $1,314.00   $1,314.10