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 $48.64   10.406%   $53.7015   $53.70   $53.70   $53.70  
  Purchase #2 $114.49   8.532%   $124.2583   $124.26   $124.25   $124.30  
  Purchase #3 $142.66   11.427%   $158.9618   $158.96   $158.95   $159.00  
  Purchase #4 $128.47   3.271%   $132.6723   $132.67   $132.65   $132.70  
  Purchase #5 $185.62   10.511%   $205.1305   $205.13   $205.15   $205.10  
  Purchase #6 $159.55   4.524%   $166.768   $166.77   $166.75   $166.80  
  Purchase #7 $200.66   6.335%   $213.3718   $213.37   $213.35   $213.40  
  7 purchase totals = $980.09       $1,054.8642   $1,054.86   $1,054.80   $1,055.00