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	$127.27	10.132%	$140.165	$140.17	$140.15	$140.20
Purchase #2	$37.72	11.401%	$42.0205	$42.02	$42.00	$42.00
Purchase #3	$13.71	4.614%	$14.3426	$14.34	$14.35	$14.30
Purchase #4	$92.85	5.686%	$98.1295	$98.13	$98.15	$98.10
Purchase #5	$12.44	3.862%	$12.9204	$12.92	$12.90	$12.90
Purchase #6	$134.34	11.343%	$149.5782	$149.58	$149.60	$149.60
Purchase #7	$158.79	3.465%	$164.2921	$164.29	$164.30	$164.30
7 purchase totals =	$577.12		$621.4483	$621.45	$621.45	$621.40