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	$122.57	6.104%	$130.0517	$130.05	$130.05	$130.10
Purchase #2	$155.50	5.581%	$164.1785	$164.18	$164.20	$164.20
Purchase #3	$94.59	9.583%	$103.6546	$103.65	$103.65	$103.70
Purchase #4	$46.32	13.216%	$52.4417	$52.44	$52.45	$52.40
Purchase #5	$134.62	12.565%	$151.535	$151.54	$151.55	$151.50
Purchase #6	$43.25	11.602%	$48.2679	$48.27	$48.25	$48.30
Purchase #7	$82.65	10.477%	$91.3092	$91.31	$91.30	$91.30
7 purchase totals =	$679.50		$741.4386	$741.44	$741.45	$741.50