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	$76.40	8.783%	$83.1102	$83.11	$83.10	$83.10
Purchase #2	$9.50	10.468%	$10.4945	$10.49	$10.50	$10.50
Purchase #3	$74.55	10.626%	$82.4717	$82.47	$82.45	$82.50
Purchase #4	$66.45	9.178%	$72.5488	$72.55	$72.55	$72.50
Purchase #5	$73.68	4.825%	$77.2351	$77.24	$77.25	$77.20
Purchase #6	$116.74	11.480%	$130.1418	$130.14	$130.15	$130.10
Purchase #7	$115.25	7.196%	$123.5434	$123.54	$123.55	$123.50
7 purchase totals =	$532.57		$579.5455	$579.54	$579.55	$579.40