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 $57.95   3.618%   $60.0466   $60.05   $60.05   $60.00  
  Purchase #2 $204.27   9.534%   $223.7451   $223.75   $223.75   $223.70  
  Purchase #3 $212.75   13.829%   $242.1712   $242.17   $242.15   $242.20  
  Purchase #4 $224.73   12.232%   $252.219   $252.22   $252.20   $252.20  
  Purchase #5 $63.71   8.240%   $68.9597   $68.96   $68.95   $69.00  
  Purchase #6 $127.29   5.602%   $134.4208   $134.42   $134.40   $134.40  
  Purchase #7 $114.54   9.358%   $125.2587   $125.26   $125.25   $125.30  
  7 purchase totals = $1,005.24       $1,106.8211   $1,106.83   $1,106.75   $1,106.80