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	$43.74	11.634%	$48.8287	$48.83	$48.85	$48.80
Purchase #2	$66.47	9.166%	$72.5626	$72.56	$72.55	$72.60
Purchase #3	$156.32	6.214%	$166.0337	$166.03	$166.05	$166.00
Purchase #4	$126.93	13.435%	$143.983	$143.98	$144.00	$144.00
Purchase #5	$33.92	9.258%	$37.0603	$37.06	$37.05	$37.10
Purchase #6	$141.71	3.130%	$146.1455	$146.15	$146.15	$146.10
Purchase #7	$173.83	6.195%	$184.5988	$184.60	$184.60	$184.60
7 purchase totals =	$742.92		$799.2126	$799.21	$799.25	$799.20