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	$126.79	13.196%	$143.5212	$143.52	$143.50	$143.50
Purchase #2	$223.52	7.874%	$241.12	$241.12	$241.10	$241.10
Purchase #3	$165.27	5.141%	$173.7665	$173.77	$173.75	$173.80
Purchase #4	$99.41	13.769%	$113.0978	$113.10	$113.10	$113.10
Purchase #5	$195.56	7.649%	$210.5184	$210.52	$210.50	$210.50
Purchase #6	$38.86	13.195%	$43.9876	$43.99	$44.00	$44.00
Purchase #7	$105.26	10.510%	$116.3228	$116.32	$116.30	$116.30
7 purchase totals =	$954.67		$1,042.3343	$1,042.34	$1,042.25	$1,042.30