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	$125.68	13.451%	$142.5852	$142.59	$142.60	$142.60
Purchase #2	$221.48	5.419%	$233.482	$233.48	$233.50	$233.50
Purchase #3	$137.35	13.505%	$155.8991	$155.90	$155.90	$155.90
Purchase #4	$153.36	5.255%	$161.4191	$161.42	$161.40	$161.40
Purchase #5	$93.63	6.589%	$99.7993	$99.80	$99.80	$99.80
Purchase #6	$48.98	6.823%	$52.3219	$52.32	$52.30	$52.30
Purchase #7	$226.60	6.680%	$241.7369	$241.74	$241.75	$241.70
7 purchase totals =	$1,007.08		$1,087.2435	$1,087.25	$1,087.25	$1,087.20