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	$151.54	5.634%	$160.0778	$160.08	$160.10	$160.10
Purchase #2	$199.81	9.731%	$219.2535	$219.25	$219.25	$219.30
Purchase #3	$55.55	6.373%	$59.0902	$59.09	$59.10	$59.10
Purchase #4	$46.63	8.344%	$50.5208	$50.52	$50.50	$50.50
Purchase #5	$20.30	10.271%	$22.385	$22.39	$22.40	$22.40
Purchase #6	$153.68	3.721%	$159.3984	$159.40	$159.40	$159.40
Purchase #7	$65.72	10.613%	$72.6949	$72.69	$72.70	$72.70
7 purchase totals =	$693.23		$743.4206	$743.42	$743.45	$743.50