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	$155.45	8.603%	$168.8234	$168.82	$168.80	$168.80
Purchase #2	$98.92	4.203%	$103.0776	$103.08	$103.10	$103.10
Purchase #3	$220.90	3.793%	$229.2787	$229.28	$229.30	$229.30
Purchase #4	$60.73	5.267%	$63.9286	$63.93	$63.95	$63.90
Purchase #5	$62.52	3.330%	$64.6019	$64.60	$64.60	$64.60
Purchase #6	$99.61	12.344%	$111.9059	$111.91	$111.90	$111.90
Purchase #7	$10.64	3.717%	$11.0355	$11.04	$11.05	$11.00
7 purchase totals =	$708.77		$752.6516	$752.66	$752.70	$752.60