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	$132.82	8.631%	$144.2837	$144.28	$144.30	$144.30
Purchase #2	$89.52	11.141%	$99.4934	$99.49	$99.50	$99.50
Purchase #3	$223.81	6.539%	$238.4449	$238.44	$238.45	$238.40
Purchase #4	$214.58	10.609%	$237.3448	$237.34	$237.35	$237.30
Purchase #5	$103.66	9.209%	$113.206	$113.21	$113.20	$113.20
Purchase #6	$226.69	10.286%	$250.0073	$250.01	$250.00	$250.00
Purchase #7	$95.66	5.869%	$101.2743	$101.27	$101.25	$101.30
7 purchase totals =	$1,086.74		$1,184.0544	$1,184.04	$1,184.05	$1,184.00