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	$166.58	13.378%	$188.8651	$188.87	$188.85	$188.90
Purchase #2	$146.33	9.743%	$160.5869	$160.59	$160.60	$160.60
Purchase #3	$183.29	13.854%	$208.683	$208.68	$208.70	$208.70
Purchase #4	$36.86	13.444%	$41.8155	$41.82	$41.80	$41.80
Purchase #5	$235.98	6.147%	$250.4857	$250.49	$250.50	$250.50
Purchase #6	$48.78	11.587%	$54.4321	$54.43	$54.45	$54.40
Purchase #7	$134.54	7.868%	$145.1256	$145.13	$145.15	$145.10
7 purchase totals =	$952.36		$1,049.9939	$1,050.01	$1,050.05	$1,050.00