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 $95.42   6.865%   $101.9706   $101.97   $101.95   $102.00  
  Purchase #2 $188.94   10.545%   $208.8637   $208.86   $208.85   $208.90  
  Purchase #3 $214.86   11.337%   $239.2187   $239.22   $239.20   $239.20  
  Purchase #4 $77.36   10.694%   $85.6329   $85.63   $85.65   $85.60  
  Purchase #5 $94.29   9.499%   $103.2466   $103.25   $103.25   $103.20  
  Purchase #6 $138.86   5.166%   $146.0335   $146.03   $146.05   $146.00  
  Purchase #7 $113.73   8.393%   $123.2754   $123.28   $123.30   $123.30  
  7 purchase totals = $923.46       $1,008.2414   $1,008.24   $1,008.25   $1,008.20