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 $214.60   13.855%   $244.3328   $244.33   $244.35   $244.30  
  Purchase #2 $53.85   4.597%   $56.3255   $56.33   $56.35   $56.30  
  Purchase #3 $161.73   13.836%   $184.107   $184.11   $184.10   $184.10  
  Purchase #4 $131.40   7.122%   $140.7583   $140.76   $140.75   $140.80  
  Purchase #5 $76.58   12.238%   $85.9519   $85.95   $85.95   $86.00  
  Purchase #6 $155.88   9.249%   $170.2973   $170.30   $170.30   $170.30  
  Purchase #7 $81.87   6.872%   $87.4961   $87.50   $87.50   $87.50  
  7 purchase totals = $875.91       $969.2689   $969.28   $969.30   $969.30