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	$151.47	11.739%	$169.2511	$169.25	$169.25	$169.30
Purchase #2	$11.32	7.749%	$12.1972	$12.20	$12.20	$12.20
Purchase #3	$83.55	8.612%	$90.7453	$90.75	$90.75	$90.70
Purchase #4	$90.86	9.689%	$99.6634	$99.66	$99.65	$99.70
Purchase #5	$38.76	12.856%	$43.743	$43.74	$43.75	$43.70
Purchase #6	$231.95	4.443%	$242.2555	$242.26	$242.25	$242.30
Purchase #7	$248.75	9.472%	$272.3116	$272.31	$272.30	$272.30
7 purchase totals =	$856.66		$930.1671	$930.17	$930.15	$930.20