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	$42.95	3.111%	$44.2862	$44.29	$44.30	$44.30
Purchase #2	$97.77	10.776%	$108.3057	$108.31	$108.30	$108.30
Purchase #3	$36.44	6.844%	$38.934	$38.93	$38.95	$38.90
Purchase #4	$20.91	6.353%	$22.2384	$22.24	$22.25	$22.20
Purchase #5	$153.68	12.109%	$172.2891	$172.29	$172.30	$172.30
Purchase #6	$69.60	12.696%	$78.4364	$78.44	$78.45	$78.40
Purchase #7	$92.97	11.608%	$103.762	$103.76	$103.75	$103.80
7 purchase totals =	$514.32		$568.2518	$568.26	$568.30	$568.20