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	$239.42	11.783%	$267.6309	$267.63	$267.65	$267.60
Purchase #2	$211.78	3.546%	$219.2897	$219.29	$219.30	$219.30
Purchase #3	$92.64	13.825%	$105.4475	$105.45	$105.45	$105.40
Purchase #4	$228.37	9.872%	$250.9147	$250.91	$250.90	$250.90
Purchase #5	$229.28	5.609%	$242.1403	$242.14	$242.15	$242.10
Purchase #6	$130.58	11.146%	$145.1344	$145.13	$145.15	$145.10
Purchase #7	$132.35	10.418%	$146.1382	$146.14	$146.15	$146.10
7 purchase totals =	$1,264.42		$1,376.6957	$1,376.69	$1,376.75	$1,376.50