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 $87.63   5.706%   $92.6302   $92.63   $92.65   $92.60  
  Purchase #2 $245.85   5.209%   $258.6563   $258.66   $258.65   $258.70  
  Purchase #3 $192.59   9.253%   $210.4104   $210.41   $210.40   $210.40  
  Purchase #4 $123.99   4.819%   $129.9651   $129.97   $129.95   $130.00  
  Purchase #5 $188.30   3.249%   $194.4179   $194.42   $194.40   $194.40  
  Purchase #6 $56.61   12.366%   $63.6104   $63.61   $63.60   $63.60  
  Purchase #7 $119.67   5.658%   $126.4409   $126.44   $126.45   $126.40  
  7 purchase totals = $1,014.64       $1,076.1312   $1,076.14   $1,076.10   $1,076.10