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 $158.99   10.345%   $175.4375   $175.44   $175.45   $175.40  
  Purchase #2 $210.85   10.702%   $233.4152   $233.42   $233.40   $233.40  
  Purchase #3 $45.78   10.778%   $50.7142   $50.71   $50.70   $50.70  
  Purchase #4 $191.89   4.635%   $200.7841   $200.78   $200.80   $200.80  
  Purchase #5 $30.54   7.597%   $32.8601   $32.86   $32.85   $32.90  
  Purchase #6 $118.68   10.155%   $130.732   $130.73   $130.75   $130.70  
  Purchase #7 $196.28   8.659%   $213.2759   $213.28   $213.30   $213.30  
  7 purchase totals = $953.01       $1,037.2190   $1,037.22   $1,037.25   $1,037.20