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	$146.83	4.454%	$153.3698	$153.37	$153.35	$153.40
Purchase #2	$126.58	10.164%	$139.4456	$139.45	$139.45	$139.40
Purchase #3	$124.84	6.227%	$132.6138	$132.61	$132.60	$132.60
Purchase #4	$220.90	9.338%	$241.5276	$241.53	$241.55	$241.50
Purchase #5	$148.95	8.597%	$161.7552	$161.76	$161.75	$161.80
Purchase #6	$206.45	9.697%	$226.4695	$226.47	$226.45	$226.50
Purchase #7	$81.33	10.838%	$90.1445	$90.14	$90.15	$90.10
7 purchase totals =	$1,055.88		$1,145.3260	$1,145.33	$1,145.30	$1,145.30