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 $112.42   11.858%   $125.7508   $125.75   $125.75   $125.80  
  Purchase #2 $183.97   4.829%   $192.8539   $192.85   $192.85   $192.90  
  Purchase #3 $163.93   13.445%   $185.9704   $185.97   $185.95   $186.00  
  Purchase #4 $105.91   6.312%   $112.595   $112.60   $112.60   $112.60  
  Purchase #5 $156.95   4.596%   $164.1634   $164.16   $164.15   $164.20  
  Purchase #6 $159.79   9.864%   $175.5517   $175.55   $175.55   $175.60  
  Purchase #7 $176.37   7.530%   $189.6507   $189.65   $189.65   $189.70  
  7 purchase totals = $1,059.34       $1,146.5359   $1,146.53   $1,146.50   $1,146.80