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	$43.49	4.331%	$45.3736	$45.37	$45.35	$45.40
Purchase #2	$12.89	13.715%	$14.6579	$14.66	$14.65	$14.70
Purchase #3	$114.28	11.789%	$127.7525	$127.75	$127.75	$127.80
Purchase #4	$50.55	8.482%	$54.8377	$54.84	$54.85	$54.80
Purchase #5	$68.80	3.510%	$71.2149	$71.21	$71.20	$71.20
Purchase #6	$153.68	13.364%	$174.2178	$174.22	$174.20	$174.20
Purchase #7	$64.26	3.382%	$66.4333	$66.43	$66.45	$66.40
7 purchase totals =	$507.95		$554.4877	$554.48	$554.45	$554.50