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	$54.97	12.522%	$61.8533	$61.85	$61.85	$61.90
Purchase #2	$141.32	8.366%	$153.1428	$153.14	$153.15	$153.10
Purchase #3	$13.65	12.188%	$15.3137	$15.31	$15.30	$15.30
Purchase #4	$70.29	4.596%	$73.5205	$73.52	$73.50	$73.50
Purchase #5	$47.56	10.791%	$52.6922	$52.69	$52.70	$52.70
Purchase #6	$207.98	10.737%	$230.3108	$230.31	$230.30	$230.30
Purchase #7	$196.83	13.701%	$223.7977	$223.80	$223.80	$223.80
7 purchase totals =	$732.60		$810.6310	$810.62	$810.60	$810.60