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 $86.70   10.726%   $95.9994   $96.00   $96.00   $96.00  
  Purchase #2 $240.40   9.182%   $262.4735   $262.47   $262.45   $262.50  
  Purchase #3 $62.94   8.221%   $68.1143   $68.11   $68.10   $68.10  
  Purchase #4 $206.40   8.554%   $224.0555   $224.06   $224.05   $224.10  
  Purchase #5 $16.49   11.119%   $18.3235   $18.32   $18.30   $18.30  
  Purchase #6 $145.27   6.596%   $154.852   $154.85   $154.85   $154.90  
  Purchase #7 $52.93   11.701%   $59.1233   $59.12   $59.10   $59.10  
  7 purchase totals = $811.13       $882.9415   $882.93   $882.85   $883.00