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	$189.48	12.537%	$213.2351	$213.24	$213.25	$213.20
Purchase #2	$9.80	6.856%	$10.4719	$10.47	$10.45	$10.50
Purchase #3	$114.91	13.459%	$130.3757	$130.38	$130.40	$130.40
Purchase #4	$20.45	3.345%	$21.1341	$21.13	$21.15	$21.10
Purchase #5	$109.42	4.388%	$114.2213	$114.22	$114.20	$114.20
Purchase #6	$152.54	4.116%	$158.8185	$158.82	$158.80	$158.80
Purchase #7	$58.72	9.798%	$64.4734	$64.47	$64.45	$64.50
7 purchase totals =	$655.32		$712.7300	$712.73	$712.70	$712.70