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 $187.50   9.867%   $206.0006   $206.00   $206.00   $206.00  
  Purchase #2 $185.59   7.187%   $198.9284   $198.93   $198.95   $198.90  
  Purchase #3 $98.93   5.339%   $104.2119   $104.21   $104.20   $104.20  
  Purchase #4 $49.93   10.759%   $55.302   $55.30   $55.30   $55.30  
  Purchase #5 $13.88   3.225%   $14.3276   $14.33   $14.35   $14.30  
  Purchase #6 $114.90   13.388%   $130.2828   $130.28   $130.30   $130.30  
  Purchase #7 $219.34   11.669%   $244.9348   $244.93   $244.95   $244.90  
  7 purchase totals = $870.07       $953.9881   $953.98   $954.05   $953.90