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	$14.78	7.225%	$15.8479	$15.85	$15.85	$15.80
Purchase #2	$85.77	5.204%	$90.2335	$90.23	$90.25	$90.20
Purchase #3	$242.45	5.289%	$255.2732	$255.27	$255.25	$255.30
Purchase #4	$240.74	4.792%	$252.2763	$252.28	$252.30	$252.30
Purchase #5	$222.85	3.277%	$230.1528	$230.15	$230.15	$230.20
Purchase #6	$72.76	12.858%	$82.1155	$82.12	$82.10	$82.10
Purchase #7	$173.59	7.718%	$186.9877	$186.99	$187.00	$187.00
7 purchase totals =	$1,052.94		$1,112.8869	$1,112.89	$1,112.90	$1,112.90