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	$175.78	8.808%	$191.2627	$191.26	$191.25	$191.30
Purchase #2	$65.25	12.246%	$73.2405	$73.24	$73.25	$73.20
Purchase #3	$80.52	12.157%	$90.3088	$90.31	$90.30	$90.30
Purchase #4	$74.81	3.568%	$77.4792	$77.48	$77.50	$77.50
Purchase #5	$224.63	13.586%	$255.1482	$255.15	$255.15	$255.10
Purchase #6	$98.34	13.514%	$111.6297	$111.63	$111.65	$111.60
Purchase #7	$32.73	5.816%	$34.6336	$34.63	$34.65	$34.60
7 purchase totals =	$752.06		$833.7027	$833.70	$833.75	$833.60