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 $22.85   7.766%   $24.6245   $24.62   $24.60   $24.60  
  Purchase #2 $220.67   5.865%   $233.6123   $233.61   $233.60   $233.60  
  Purchase #3 $169.92   8.863%   $184.98   $184.98   $185.00   $185.00  
  Purchase #4 $205.91   9.565%   $225.6053   $225.61   $225.60   $225.60  
  Purchase #5 $172.58   11.252%   $191.9987   $192.00   $192.00   $192.00  
  Purchase #6 $150.99   7.220%   $161.8915   $161.89   $161.90   $161.90  
  Purchase #7 $42.63   8.805%   $46.3836   $46.38   $46.40   $46.40  
  7 purchase totals = $985.55       $1,069.0959   $1,069.09   $1,069.10   $1,069.10