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 $223.94   4.364%   $233.7127   $233.71   $233.70   $233.70  
  Purchase #2 $224.60   11.697%   $250.8715   $250.87   $250.85   $250.90  
  Purchase #3 $237.82   6.823%   $254.0465   $254.05   $254.05   $254.00  
  Purchase #4 $56.42   6.831%   $60.2741   $60.27   $60.25   $60.30  
  Purchase #5 $180.31   4.509%   $188.4402   $188.44   $188.45   $188.40  
  Purchase #6 $185.45   11.464%   $206.71   $206.71   $206.70   $206.70  
  Purchase #7 $158.56   5.605%   $167.4473   $167.45   $167.45   $167.40  
  7 purchase totals = $1,267.10       $1,361.5023   $1,361.50   $1,361.45   $1,361.40