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	$146.94	4.137%	$153.0189	$153.02	$153.00	$153.00
Purchase #2	$74.45	6.329%	$79.1619	$79.16	$79.15	$79.20
Purchase #3	$192.94	11.363%	$214.8638	$214.86	$214.85	$214.90
Purchase #4	$125.35	10.199%	$138.1344	$138.13	$138.15	$138.10
Purchase #5	$64.51	11.689%	$72.0506	$72.05	$72.05	$72.10
Purchase #6	$53.85	9.630%	$59.0358	$59.04	$59.05	$59.00
Purchase #7	$207.29	7.378%	$222.5839	$222.58	$222.60	$222.60
7 purchase totals =	$865.33		$938.8493	$938.84	$938.85	$938.90