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	$132.26	13.535%	$150.1614	$150.16	$150.15	$150.20
Purchase #2	$164.73	11.624%	$183.8782	$183.88	$183.90	$183.90
Purchase #3	$103.40	7.491%	$111.1457	$111.15	$111.15	$111.10
Purchase #4	$232.49	5.404%	$245.0538	$245.05	$245.05	$245.10
Purchase #5	$34.45	6.286%	$36.6155	$36.62	$36.60	$36.60
Purchase #6	$150.53	9.307%	$164.5398	$164.54	$164.55	$164.50
Purchase #7	$231.60	7.869%	$249.8246	$249.82	$249.80	$249.80
7 purchase totals =	$1,049.46		$1,141.2190	$1,141.22	$1,141.20	$1,141.20