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	$150.87	4.198%	$157.2035	$157.20	$157.20	$157.20
Purchase #2	$100.60	4.820%	$105.4489	$105.45	$105.45	$105.40
Purchase #3	$166.83	10.279%	$183.9785	$183.98	$184.00	$184.00
Purchase #4	$137.49	11.674%	$153.5406	$153.54	$153.55	$153.50
Purchase #5	$21.63	11.323%	$24.0792	$24.08	$24.10	$24.10
Purchase #6	$176.91	4.512%	$184.8922	$184.89	$184.90	$184.90
Purchase #7	$34.52	7.164%	$36.993	$36.99	$37.00	$37.00
7 purchase totals =	$788.85		$846.1359	$846.13	$846.20	$846.10