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 $56.44   10.829%   $62.5519   $62.55   $62.55   $62.60  
  Purchase #2 $216.71   10.435%   $239.3237   $239.32   $239.30   $239.30  
  Purchase #3 $185.31   6.808%   $197.9259   $197.93   $197.95   $197.90  
  Purchase #4 $196.73   13.464%   $223.2177   $223.22   $223.20   $223.20  
  Purchase #5 $223.97   6.211%   $237.8808   $237.88   $237.90   $237.90  
  Purchase #6 $78.43   3.161%   $80.9092   $80.91   $80.90   $80.90  
  Purchase #7 $159.58   4.212%   $166.3015   $166.30   $166.30   $166.30  
  7 purchase totals = $1,117.17       $1,208.1107   $1,208.11   $1,208.10   $1,208.10