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	$208.72	3.685%	$216.4113	$216.41	$216.40	$216.40
Purchase #2	$128.34	12.224%	$144.0283	$144.03	$144.05	$144.00
Purchase #3	$58.79	9.743%	$64.5179	$64.52	$64.50	$64.50
Purchase #4	$156.70	10.237%	$172.7414	$172.74	$172.75	$172.70
Purchase #5	$192.76	13.766%	$219.2953	$219.30	$219.30	$219.30
Purchase #6	$67.50	8.298%	$73.1012	$73.10	$73.10	$73.10
Purchase #7	$74.65	11.793%	$83.4535	$83.45	$83.45	$83.50
7 purchase totals =	$887.46		$973.5489	$973.55	$973.55	$973.50