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 $216.85   3.182%   $223.7502   $223.75   $223.75   $223.80  
  Purchase #2 $134.47   13.332%   $152.3975   $152.40   $152.40   $152.40  
  Purchase #3 $199.25   4.475%   $208.1664   $208.17   $208.15   $208.20  
  Purchase #4 $69.49   5.332%   $73.1952   $73.20   $73.20   $73.20  
  Purchase #5 $231.88   5.395%   $244.3899   $244.39   $244.40   $244.40  
  Purchase #6 $108.32   6.282%   $115.1247   $115.12   $115.10   $115.10  
  Purchase #7 $223.74   11.861%   $250.2778   $250.28   $250.30   $250.30  
  7 purchase totals = $1,184.00       $1,267.3017   $1,267.31   $1,267.30   $1,267.40