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	$133.68	8.821%	$145.4719	$145.47	$145.45	$145.50
Purchase #2	$47.50	3.304%	$49.0694	$49.07	$49.05	$49.10
Purchase #3	$40.30	7.449%	$43.3019	$43.30	$43.30	$43.30
Purchase #4	$89.96	4.232%	$93.7671	$93.77	$93.75	$93.80
Purchase #5	$39.79	8.873%	$43.3206	$43.32	$43.30	$43.30
Purchase #6	$111.92	13.673%	$127.2228	$127.22	$127.20	$127.20
Purchase #7	$49.67	11.171%	$55.2186	$55.22	$55.20	$55.20
7 purchase totals =	$512.82		$557.3723	$557.37	$557.25	$557.40