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	$74.68	4.748%	$78.2258	$78.23	$78.25	$78.20
Purchase #2	$177.85	7.788%	$191.701	$191.70	$191.70	$191.70
Purchase #3	$226.87	12.436%	$255.0836	$255.08	$255.10	$255.10
Purchase #4	$228.62	12.200%	$256.5116	$256.51	$256.50	$256.50
Purchase #5	$247.40	6.561%	$263.6319	$263.63	$263.65	$263.60
Purchase #6	$146.80	13.677%	$166.8778	$166.88	$166.90	$166.90
Purchase #7	$207.48	4.655%	$217.1382	$217.14	$217.15	$217.10
7 purchase totals =	$1,309.70		$1,429.1699	$1,429.17	$1,429.25	$1,429.10