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 $193.71   10.721%   $214.4776   $214.48   $214.50   $214.50  
  Purchase #2 $248.34   4.103%   $258.5294   $258.53   $258.55   $258.50  
  Purchase #3 $74.79   3.359%   $77.3022   $77.30   $77.30   $77.30  
  Purchase #4 $163.66   3.177%   $168.8595   $168.86   $168.85   $168.90  
  Purchase #5 $81.87   4.375%   $85.4518   $85.45   $85.45   $85.50  
  Purchase #6 $217.91   13.191%   $246.6545   $246.65   $246.65   $246.70  
  Purchase #7 $55.81   6.251%   $59.2987   $59.30   $59.30   $59.30  
  7 purchase totals = $1,036.09       $1,110.5737   $1,110.57   $1,110.60   $1,110.70