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	$149.92	3.279%	$154.8359	$154.84	$154.85	$154.80
Purchase #2	$90.76	10.867%	$100.6229	$100.62	$100.60	$100.60
Purchase #3	$184.78	6.142%	$196.1292	$196.13	$196.15	$196.10
Purchase #4	$99.91	11.450%	$111.3497	$111.35	$111.35	$111.30
Purchase #5	$106.64	6.603%	$113.6814	$113.68	$113.70	$113.70
Purchase #6	$120.78	5.398%	$127.2997	$127.30	$127.30	$127.30
Purchase #7	$21.28	5.630%	$22.4781	$22.48	$22.50	$22.50
7 purchase totals =	$774.07		$826.3969	$826.40	$826.45	$826.30