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	$49.61	4.661%	$51.9223	$51.92	$51.90	$51.90
Purchase #2	$228.78	10.784%	$253.4516	$253.45	$253.45	$253.50
Purchase #3	$133.98	10.138%	$147.5629	$147.56	$147.55	$147.60
Purchase #4	$160.32	7.687%	$172.6438	$172.64	$172.65	$172.60
Purchase #5	$224.93	13.439%	$255.1583	$255.16	$255.15	$255.20
Purchase #6	$42.30	9.516%	$46.3253	$46.33	$46.35	$46.30
Purchase #7	$30.52	5.516%	$32.2035	$32.20	$32.20	$32.20
7 purchase totals =	$870.44		$959.2677	$959.26	$959.25	$959.30