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	$152.69	12.807%	$172.245	$172.25	$172.25	$172.20
Purchase #2	$126.29	4.789%	$132.338	$132.34	$132.35	$132.30
Purchase #3	$228.46	11.468%	$254.6598	$254.66	$254.65	$254.70
Purchase #4	$122.67	3.794%	$127.3241	$127.32	$127.30	$127.30
Purchase #5	$180.30	12.242%	$202.3723	$202.37	$202.35	$202.40
Purchase #6	$110.38	5.272%	$116.1992	$116.20	$116.20	$116.20
Purchase #7	$112.85	13.181%	$127.7248	$127.72	$127.70	$127.70
7 purchase totals =	$1,033.64		$1,132.8632	$1,132.86	$1,132.80	$1,132.80