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 $74.28   11.267%   $82.6491   $82.65   $82.65   $82.60  
  Purchase #2 $241.67   8.329%   $261.7987   $261.80   $261.80   $261.80  
  Purchase #3 $68.73   10.240%   $75.768   $75.77   $75.75   $75.80  
  Purchase #4 $189.67   13.304%   $214.9037   $214.90   $214.90   $214.90  
  Purchase #5 $236.80   5.114%   $248.91   $248.91   $248.90   $248.90  
  Purchase #6 $103.96   12.362%   $116.8115   $116.81   $116.80   $116.80  
  Purchase #7 $107.64   10.471%   $118.911   $118.91   $118.90   $118.90  
  7 purchase totals = $1,022.75       $1,119.7520   $1,119.75   $1,119.70   $1,119.70