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	$13.48	6.710%	$14.3845	$14.38	$14.40	$14.40
Purchase #2	$245.54	5.690%	$259.5112	$259.51	$259.50	$259.50
Purchase #3	$187.92	13.486%	$213.2629	$213.26	$213.25	$213.30
Purchase #4	$211.63	7.669%	$227.8599	$227.86	$227.85	$227.90
Purchase #5	$121.48	12.724%	$136.9371	$136.94	$136.95	$136.90
Purchase #6	$208.86	3.373%	$215.9048	$215.90	$215.90	$215.90
Purchase #7	$145.89	13.507%	$165.5954	$165.60	$165.60	$165.60
7 purchase totals =	$1,134.80		$1,233.4558	$1,233.45	$1,233.45	$1,233.50