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	$166.82	3.238%	$172.2216	$172.22	$172.20	$172.20
Purchase #2	$9.41	12.384%	$10.5753	$10.58	$10.60	$10.60
Purchase #3	$65.66	11.134%	$72.9706	$72.97	$72.95	$73.00
Purchase #4	$133.69	11.732%	$149.3745	$149.37	$149.35	$149.40
Purchase #5	$96.88	12.216%	$108.7149	$108.71	$108.70	$108.70
Purchase #6	$60.48	10.150%	$66.6187	$66.62	$66.60	$66.60
Purchase #7	$40.68	12.104%	$45.6039	$45.60	$45.60	$45.60
7 purchase totals =	$573.62		$626.0795	$626.07	$626.00	$626.10