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 $86.48   10.866%   $95.8769   $95.88   $95.90   $95.90  
  Purchase #2 $217.34   12.149%   $243.7446   $243.74   $243.75   $243.70  
  Purchase #3 $15.44   10.442%   $17.0522   $17.05   $17.05   $17.10  
  Purchase #4 $183.89   4.177%   $191.5711   $191.57   $191.55   $191.60  
  Purchase #5 $116.64   6.866%   $124.6485   $124.65   $124.65   $124.60  
  Purchase #6 $160.64   9.810%   $176.3988   $176.40   $176.40   $176.40  
  Purchase #7 $31.50   5.174%   $33.1298   $33.13   $33.15   $33.10  
  7 purchase totals = $811.93       $882.4219   $882.42   $882.45   $882.40