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 $192.51   11.263%   $214.1924   $214.19   $214.20   $214.20  
  Purchase #2 $68.34   12.201%   $76.6782   $76.68   $76.70   $76.70  
  Purchase #3 $243.35   7.803%   $262.3386   $262.34   $262.35   $262.30  
  Purchase #4 $190.62   7.862%   $205.6065   $205.61   $205.60   $205.60  
  Purchase #5 $101.75   9.521%   $111.4376   $111.44   $111.45   $111.40  
  Purchase #6 $202.39   13.763%   $230.2449   $230.24   $230.25   $230.20  
  Purchase #7 $28.40   11.622%   $31.7006   $31.70   $31.70   $31.70  
  7 purchase totals = $1,027.36       $1,132.1988   $1,132.20   $1,132.25   $1,132.10