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	$146.62	13.527%	$166.4533	$166.45	$166.45	$166.50
Purchase #2	$35.92	6.660%	$38.3123	$38.31	$38.30	$38.30
Purchase #3	$155.73	12.217%	$174.7555	$174.76	$174.75	$174.80
Purchase #4	$240.36	4.831%	$251.9718	$251.97	$251.95	$252.00
Purchase #5	$163.93	13.602%	$186.2278	$186.23	$186.25	$186.20
Purchase #6	$80.73	12.401%	$90.7413	$90.74	$90.75	$90.70
Purchase #7	$143.41	6.844%	$153.225	$153.23	$153.25	$153.20
7 purchase totals =	$966.70		$1,061.6870	$1,061.69	$1,061.70	$1,061.70