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	$133.39	8.869%	$145.2204	$145.22	$145.20	$145.20
Purchase #2	$94.42	5.313%	$99.4365	$99.44	$99.45	$99.40
Purchase #3	$75.67	10.586%	$83.6804	$83.68	$83.70	$83.70
Purchase #4	$102.55	9.460%	$112.2512	$112.25	$112.25	$112.30
Purchase #5	$42.58	7.363%	$45.7152	$45.72	$45.70	$45.70
Purchase #6	$96.50	3.634%	$100.0068	$100.01	$100.00	$100.00
Purchase #7	$34.83	6.408%	$37.0619	$37.06	$37.05	$37.10
7 purchase totals =	$579.94		$623.3724	$623.38	$623.35	$623.40