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	$105.43	10.851%	$116.8702	$116.87	$116.85	$116.90
Purchase #2	$92.50	4.244%	$96.4257	$96.43	$96.45	$96.40
Purchase #3	$8.28	9.255%	$9.0463	$9.05	$9.05	$9.00
Purchase #4	$55.34	3.765%	$57.4236	$57.42	$57.40	$57.40
Purchase #5	$218.90	9.709%	$240.153	$240.15	$240.15	$240.20
Purchase #6	$111.36	4.754%	$116.6541	$116.65	$116.65	$116.70
Purchase #7	$92.75	7.105%	$99.3399	$99.34	$99.35	$99.30
7 purchase totals =	$684.56		$735.9128	$735.91	$735.90	$735.90