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 $214.54   8.869%   $233.5676   $233.57   $233.55   $233.60  
  Purchase #2 $87.93   8.226%   $95.1631   $95.16   $95.15   $95.20  
  Purchase #3 $242.83   5.438%   $256.0351   $256.04   $256.05   $256.00  
  Purchase #4 $208.73   7.579%   $224.5496   $224.55   $224.55   $224.50  
  Purchase #5 $116.90   3.862%   $121.4147   $121.41   $121.40   $121.40  
  Purchase #6 $187.29   12.359%   $210.4372   $210.44   $210.45   $210.40  
  Purchase #7 $161.51   12.435%   $181.5938   $181.59   $181.60   $181.60  
  7 purchase totals = $1,219.73       $1,322.7611   $1,322.76   $1,322.75   $1,322.70