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	$71.52	6.521%	$76.1838	$76.18	$76.20	$76.20
Purchase #2	$105.32	6.837%	$112.5207	$112.52	$112.50	$112.50
Purchase #3	$155.73	11.797%	$174.1015	$174.10	$174.10	$174.10
Purchase #4	$124.34	10.852%	$137.8334	$137.83	$137.85	$137.80
Purchase #5	$90.26	10.304%	$99.5604	$99.56	$99.55	$99.60
Purchase #6	$246.69	13.358%	$279.6429	$279.64	$279.65	$279.60
Purchase #7	$200.70	13.680%	$228.1558	$228.16	$228.15	$228.20
7 purchase totals =	$994.56		$1,107.9985	$1,107.99	$1,108.00	$1,108.00