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 $59.61   4.428%   $62.2495   $62.25   $62.25   $62.20  
  Purchase #2 $78.49   10.852%   $87.0077   $87.01   $87.00   $87.00  
  Purchase #3 $41.41   10.354%   $45.6976   $45.70   $45.70   $45.70  
  Purchase #4 $78.62   6.171%   $83.4716   $83.47   $83.45   $83.50  
  Purchase #5 $171.53   7.405%   $184.2318   $184.23   $184.25   $184.20  
  Purchase #6 $5.85   6.727%   $6.2435   $6.24   $6.25   $6.20  
  Purchase #7 $239.51   9.502%   $262.2682   $262.27   $262.25   $262.30  
  7 purchase totals = $675.02       $731.1699   $731.17   $731.15   $731.10