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 $60.90   3.486%   $63.023   $63.02   $63.00   $63.00  
  Purchase #2 $75.70   10.438%   $83.6016   $83.60   $83.60   $83.60  
  Purchase #3 $201.85   3.335%   $208.5817   $208.58   $208.60   $208.60  
  Purchase #4 $185.89   4.442%   $194.1472   $194.15   $194.15   $194.10  
  Purchase #5 $147.82   11.231%   $164.4217   $164.42   $164.40   $164.40  
  Purchase #6 $221.60   5.251%   $233.2362   $233.24   $233.25   $233.20  
  Purchase #7 $237.81   7.462%   $255.5554   $255.56   $255.55   $255.60  
  7 purchase totals = $1,131.57       $1,202.5668   $1,202.57   $1,202.55   $1,202.50