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 $194.32   5.522%   $205.0504   $205.05   $205.05   $205.10  
  Purchase #2 $216.66   5.525%   $228.6305   $228.63   $228.65   $228.60  
  Purchase #3 $66.40   7.614%   $71.4557   $71.46   $71.45   $71.50  
  Purchase #4 $240.34   6.108%   $255.02   $255.02   $255.00   $255.00  
  Purchase #5 $123.60   11.223%   $137.4716   $137.47   $137.45   $137.50  
  Purchase #6 $239.30   7.524%   $257.3049   $257.30   $257.30   $257.30  
  Purchase #7 $234.58   3.179%   $242.0373   $242.04   $242.05   $242.00  
  7 purchase totals = $1,315.20       $1,396.9704   $1,396.97   $1,396.95   $1,397.00