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 $236.59   3.315%   $244.433   $244.43   $244.45   $244.40  
  Purchase #2 $199.69   7.206%   $214.0797   $214.08   $214.10   $214.10  
  Purchase #3 $198.41   9.567%   $217.3919   $217.39   $217.40   $217.40  
  Purchase #4 $72.30   6.172%   $76.7624   $76.76   $76.75   $76.80  
  Purchase #5 $226.95   9.326%   $248.1154   $248.12   $248.10   $248.10  
  Purchase #6 $54.41   9.215%   $59.4239   $59.42   $59.40   $59.40  
  Purchase #7 $208.86   11.747%   $233.3948   $233.39   $233.40   $233.40  
  7 purchase totals = $1,197.21       $1,293.6011   $1,293.59   $1,293.60   $1,293.60