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 $201.39   11.236%   $224.0182   $224.02   $224.00   $224.00  
  Purchase #2 $60.96   11.844%   $68.1801   $68.18   $68.20   $68.20  
  Purchase #3 $125.38   7.335%   $134.5766   $134.58   $134.60   $134.60  
  Purchase #4 $63.28   9.484%   $69.2815   $69.28   $69.30   $69.30  
  Purchase #5 $216.50   10.545%   $239.3299   $239.33   $239.35   $239.30  
  Purchase #6 $207.98   8.102%   $224.8305   $224.83   $224.85   $224.80  
  Purchase #7 $126.46   6.128%   $134.2095   $134.21   $134.20   $134.20  
  7 purchase totals = $1,001.95       $1,094.4263   $1,094.43   $1,094.50   $1,094.40