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	$77.76	10.677%	$86.0624	$86.06	$86.05	$86.10
Purchase #2	$103.59	4.447%	$108.1966	$108.20	$108.20	$108.20
Purchase #3	$101.84	9.209%	$111.2184	$111.22	$111.20	$111.20
Purchase #4	$211.74	13.473%	$240.2677	$240.27	$240.25	$240.30
Purchase #5	$231.98	4.435%	$242.2683	$242.27	$242.25	$242.30
Purchase #6	$130.82	12.239%	$146.8311	$146.83	$146.85	$146.80
Purchase #7	$194.75	11.344%	$216.8424	$216.84	$216.85	$216.80
7 purchase totals =	$1,052.48		$1,151.6869	$1,151.69	$1,151.65	$1,151.70