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 $86.40   10.278%   $95.2802   $95.28   $95.30   $95.30  
  Purchase #2 $69.80   7.505%   $75.0385   $75.04   $75.05   $75.00  
  Purchase #3 $113.67   13.761%   $129.3121   $129.31   $129.30   $129.30  
  Purchase #4 $204.91   4.659%   $214.4568   $214.46   $214.45   $214.50  
  Purchase #5 $50.86   9.770%   $55.829   $55.83   $55.85   $55.80  
  Purchase #6 $215.58   12.698%   $242.9543   $242.95   $242.95   $243.00  
  Purchase #7 $226.90   9.663%   $248.8253   $248.83   $248.85   $248.80  
  7 purchase totals = $968.12       $1,061.6962   $1,061.70   $1,061.75   $1,061.70