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 $91.58   4.566%   $95.7615   $95.76   $95.75   $95.80  
  Purchase #2 $232.54   7.580%   $250.1665   $250.17   $250.15   $250.20  
  Purchase #3 $106.96   7.812%   $115.3157   $115.32   $115.30   $115.30  
  Purchase #4 $207.69   12.243%   $233.1175   $233.12   $233.10   $233.10  
  Purchase #5 $208.71   11.379%   $232.4591   $232.46   $232.45   $232.50  
  Purchase #6 $203.79   5.291%   $214.5725   $214.57   $214.55   $214.60  
  Purchase #7 $143.48   12.170%   $160.9415   $160.94   $160.95   $160.90  
  7 purchase totals = $1,194.75       $1,302.3343   $1,302.34   $1,302.25   $1,302.40