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 $62.95   10.849%   $69.7794   $69.78   $69.80   $69.80  
  Purchase #2 $158.30   8.468%   $171.7048   $171.70   $171.70   $171.70  
  Purchase #3 $183.73   6.205%   $195.1304   $195.13   $195.15   $195.10  
  Purchase #4 $192.62   3.193%   $198.7704   $198.77   $198.75   $198.80  
  Purchase #5 $72.25   12.505%   $81.2849   $81.28   $81.30   $81.30  
  Purchase #6 $228.40   3.498%   $236.3894   $236.39   $236.40   $236.40  
  Purchase #7 $144.37   9.573%   $158.1905   $158.19   $158.20   $158.20  
  7 purchase totals = $1,042.62       $1,111.2498   $1,111.24   $1,111.30   $1,111.30