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	$165.54	3.732%	$171.718	$171.72	$171.70	$171.70
Purchase #2	$116.50	9.204%	$127.2227	$127.22	$127.20	$127.20
Purchase #3	$103.81	7.423%	$111.5158	$111.52	$111.50	$111.50
Purchase #4	$96.57	13.593%	$109.6968	$109.70	$109.70	$109.70
Purchase #5	$250.83	12.399%	$281.9304	$281.93	$281.95	$281.90
Purchase #6	$30.91	9.198%	$33.7531	$33.75	$33.75	$33.80
Purchase #7	$155.48	10.728%	$172.1599	$172.16	$172.15	$172.20
7 purchase totals =	$919.64		$1,007.9967	$1,008.00	$1,007.95	$1,008.00