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 $195.46   6.813%   $208.7767   $208.78   $208.80   $208.80  
  Purchase #2 $30.96   11.796%   $34.612   $34.61   $34.60   $34.60  
  Purchase #3 $127.59   11.392%   $142.1251   $142.13   $142.15   $142.10  
  Purchase #4 $249.54   8.564%   $270.9106   $270.91   $270.90   $270.90  
  Purchase #5 $195.82   8.159%   $211.797   $211.80   $211.80   $211.80  
  Purchase #6 $64.80   5.764%   $68.5351   $68.54   $68.55   $68.50  
  Purchase #7 $94.94   12.854%   $107.1436   $107.14   $107.15   $107.10  
  7 purchase totals = $959.11       $1,043.9001   $1,043.91   $1,043.95   $1,043.80