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	$77.68	10.784%	$86.057	$86.06	$86.05	$86.10
Purchase #2	$232.59	13.717%	$264.4944	$264.49	$264.50	$264.50
Purchase #3	$109.51	6.644%	$116.7858	$116.79	$116.80	$116.80
Purchase #4	$141.78	3.169%	$146.273	$146.27	$146.25	$146.30
Purchase #5	$139.36	10.198%	$153.5719	$153.57	$153.55	$153.60
Purchase #6	$134.79	6.323%	$143.3128	$143.31	$143.30	$143.30
Purchase #7	$58.43	13.252%	$66.1731	$66.17	$66.15	$66.20
7 purchase totals =	$894.14		$976.6680	$976.66	$976.60	$976.80