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	$144.39	12.836%	$162.9239	$162.92	$162.90	$162.90
Purchase #2	$50.32	7.142%	$53.9139	$53.91	$53.90	$53.90
Purchase #3	$121.28	11.235%	$134.9058	$134.91	$134.90	$134.90
Purchase #4	$92.49	9.757%	$101.5142	$101.51	$101.50	$101.50
Purchase #5	$90.29	10.196%	$99.496	$99.50	$99.50	$99.50
Purchase #6	$135.27	13.857%	$154.0144	$154.01	$154.00	$154.00
Purchase #7	$49.54	6.521%	$52.7705	$52.77	$52.75	$52.80
7 purchase totals =	$683.58		$759.5387	$759.53	$759.45	$759.50