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 $86.75   9.752%   $95.2099   $95.21   $95.20   $95.20  
  Purchase #2 $241.43   5.435%   $254.5517   $254.55   $254.55   $254.60  
  Purchase #3 $102.77   10.711%   $113.7777   $113.78   $113.80   $113.80  
  Purchase #4 $80.41   5.279%   $84.6548   $84.65   $84.65   $84.70  
  Purchase #5 $190.66   8.202%   $206.2979   $206.30   $206.30   $206.30  
  Purchase #6 $167.86   10.763%   $185.9268   $185.93   $185.95   $185.90  
  Purchase #7 $185.46   7.572%   $199.503   $199.50   $199.50   $199.50  
  7 purchase totals = $1,055.34       $1,139.9218   $1,139.92   $1,139.95   $1,140.00