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 $67.99   5.562%   $71.7716   $71.77   $71.75   $71.80  
  Purchase #2 $219.47   11.610%   $244.9505   $244.95   $244.95   $245.00  
  Purchase #3 $56.50   6.146%   $59.9725   $59.97   $59.95   $60.00  
  Purchase #4 $42.71   8.436%   $46.313   $46.31   $46.30   $46.30  
  Purchase #5 $199.50   5.308%   $210.0895   $210.09   $210.10   $210.10  
  Purchase #6 $110.84   3.491%   $114.7094   $114.71   $114.70   $114.70  
  Purchase #7 $150.96   3.615%   $156.4172   $156.42   $156.40   $156.40  
  7 purchase totals = $847.97       $904.2237   $904.22   $904.15   $904.30