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 $73.39   3.712%   $76.1142   $76.11   $76.10   $76.10  
  Purchase #2 $54.86   5.245%   $57.7374   $57.74   $57.75   $57.70  
  Purchase #3 $216.49   3.379%   $223.8052   $223.81   $223.80   $223.80  
  Purchase #4 $87.57   8.223%   $94.7709   $94.77   $94.75   $94.80  
  Purchase #5 $178.50   12.601%   $200.9928   $200.99   $201.00   $201.00  
  Purchase #6 $173.66   6.734%   $185.3543   $185.35   $185.35   $185.40  
  Purchase #7 $140.62   4.389%   $146.7918   $146.79   $146.80   $146.80  
  7 purchase totals = $925.09       $985.5666   $985.56   $985.55   $985.60