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 $72.85   5.563%   $76.9026   $76.90   $76.90   $76.90  
  Purchase #2 $223.35   12.545%   $251.3693   $251.37   $251.35   $251.40  
  Purchase #3 $108.70   9.232%   $118.7352   $118.74   $118.75   $118.70  
  Purchase #4 $203.86   3.736%   $211.4762   $211.48   $211.50   $211.50  
  Purchase #5 $249.87   12.648%   $281.4736   $281.47   $281.45   $281.50  
  Purchase #6 $248.49   3.223%   $256.4988   $256.50   $256.50   $256.50  
  Purchase #7 $172.59   7.335%   $185.2495   $185.25   $185.25   $185.20  
  7 purchase totals = $1,279.71       $1,381.7052   $1,381.71   $1,381.70   $1,381.70