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	$238.29	5.521%	$251.446	$251.45	$251.45	$251.40
Purchase #2	$134.94	4.590%	$141.1337	$141.13	$141.15	$141.10
Purchase #3	$98.92	12.272%	$111.0595	$111.06	$111.05	$111.10
Purchase #4	$18.66	9.486%	$20.4301	$20.43	$20.45	$20.40
Purchase #5	$132.91	13.780%	$151.225	$151.23	$151.25	$151.20
Purchase #6	$220.93	7.226%	$236.8944	$236.89	$236.90	$236.90
Purchase #7	$196.79	4.229%	$205.1122	$205.11	$205.10	$205.10
7 purchase totals =	$1,041.44		$1,117.3009	$1,117.30	$1,117.35	$1,117.20