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	$61.41	5.741%	$64.9355	$64.94	$64.95	$64.90
Purchase #2	$143.30	8.432%	$155.3831	$155.38	$155.40	$155.40
Purchase #3	$145.27	5.540%	$153.318	$153.32	$153.30	$153.30
Purchase #4	$48.48	11.865%	$54.2322	$54.23	$54.25	$54.20
Purchase #5	$49.33	6.434%	$52.5039	$52.50	$52.50	$52.50
Purchase #6	$231.65	4.726%	$242.5978	$242.60	$242.60	$242.60
Purchase #7	$221.49	7.659%	$238.4539	$238.45	$238.45	$238.50
7 purchase totals =	$900.93		$961.4244	$961.42	$961.45	$961.40