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	$215.88	3.501%	$223.438	$223.44	$223.45	$223.40
Purchase #2	$208.83	5.786%	$220.9129	$220.91	$220.90	$220.90
Purchase #3	$10.95	7.494%	$11.7706	$11.77	$11.75	$11.80
Purchase #4	$102.58	10.230%	$113.0739	$113.07	$113.05	$113.10
Purchase #5	$36.52	12.723%	$41.1664	$41.17	$41.15	$41.20
Purchase #6	$151.43	13.635%	$172.0775	$172.08	$172.10	$172.10
Purchase #7	$220.52	7.254%	$236.5165	$236.52	$236.50	$236.50
7 purchase totals =	$946.71		$1,018.9558	$1,018.96	$1,018.90	$1,019.00