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	$211.34	8.573%	$229.4582	$229.46	$229.45	$229.50
Purchase #2	$88.54	13.593%	$100.5752	$100.58	$100.60	$100.60
Purchase #3	$212.44	10.736%	$235.2476	$235.25	$235.25	$235.20
Purchase #4	$87.97	4.195%	$91.6603	$91.66	$91.65	$91.70
Purchase #5	$170.73	8.525%	$185.2847	$185.28	$185.30	$185.30
Purchase #6	$117.37	5.724%	$124.0883	$124.09	$124.10	$124.10
Purchase #7	$228.98	11.752%	$255.8897	$255.89	$255.90	$255.90
7 purchase totals =	$1,117.37		$1,222.2040	$1,222.21	$1,222.25	$1,222.30