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 $210.37   10.856%   $233.2078   $233.21   $233.20   $233.20  
  Purchase #2 $122.54   8.172%   $132.554   $132.55   $132.55   $132.60  
  Purchase #3 $141.61   3.224%   $146.1755   $146.18   $146.20   $146.20  
  Purchase #4 $143.53   10.610%   $158.7585   $158.76   $158.75   $158.80  
  Purchase #5 $214.76   6.347%   $228.3908   $228.39   $228.40   $228.40  
  Purchase #6 $232.59   12.821%   $262.4104   $262.41   $262.40   $262.40  
  Purchase #7 $185.61   11.407%   $206.7825   $206.78   $206.80   $206.80  
  7 purchase totals = $1,251.01       $1,368.2795   $1,368.28   $1,368.30   $1,368.40