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 $205.44   4.483%   $214.6499   $214.65   $214.65   $214.60  
  Purchase #2 $227.43   7.416%   $244.2962   $244.30   $244.30   $244.30  
  Purchase #3 $89.86   13.792%   $102.2535   $102.25   $102.25   $102.30  
  Purchase #4 $151.85   13.736%   $172.7081   $172.71   $172.70   $172.70  
  Purchase #5 $110.91   5.417%   $116.918   $116.92   $116.90   $116.90  
  Purchase #6 $23.40   13.806%   $26.6306   $26.63   $26.65   $26.60  
  Purchase #7 $209.57   11.387%   $233.4337   $233.43   $233.45   $233.40  
  7 purchase totals = $1,018.46       $1,110.8900   $1,110.89   $1,110.90   $1,110.80