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	$175.74	9.743%	$192.8623	$192.86	$192.85	$192.90
Purchase #2	$188.97	5.377%	$199.1309	$199.13	$199.15	$199.10
Purchase #3	$39.92	6.515%	$42.5208	$42.52	$42.50	$42.50
Purchase #4	$34.35	8.522%	$37.2773	$37.28	$37.30	$37.30
Purchase #5	$158.28	9.655%	$173.5619	$173.56	$173.55	$173.60
Purchase #6	$98.80	12.675%	$111.3229	$111.32	$111.30	$111.30
Purchase #7	$104.98	9.789%	$115.2565	$115.26	$115.25	$115.30
7 purchase totals =	$801.04		$871.9326	$871.93	$871.90	$872.00