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	$195.52	4.262%	$203.8531	$203.85	$203.85	$203.90
Purchase #2	$26.26	4.671%	$27.4866	$27.49	$27.50	$27.50
Purchase #3	$53.37	10.653%	$59.0555	$59.06	$59.05	$59.10
Purchase #4	$74.40	12.588%	$83.7655	$83.77	$83.75	$83.80
Purchase #5	$57.74	11.636%	$64.4586	$64.46	$64.45	$64.50
Purchase #6	$137.32	10.113%	$151.2072	$151.21	$151.20	$151.20
Purchase #7	$96.41	5.476%	$101.6894	$101.69	$101.70	$101.70
7 purchase totals =	$641.02		$691.5159	$691.53	$691.50	$691.70