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	$56.68	8.406%	$61.4445	$61.44	$61.45	$61.40
Purchase #2	$142.98	10.823%	$158.4547	$158.45	$158.45	$158.50
Purchase #3	$52.89	10.210%	$58.2901	$58.29	$58.30	$58.30
Purchase #4	$123.69	5.513%	$130.509	$130.51	$130.50	$130.50
Purchase #5	$50.94	4.370%	$53.1661	$53.17	$53.15	$53.20
Purchase #6	$239.54	10.866%	$265.5684	$265.57	$265.55	$265.60
Purchase #7	$105.75	13.617%	$120.15	$120.15	$120.15	$120.20
7 purchase totals =	$772.47		$847.5828	$847.58	$847.55	$847.70