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	$241.84	11.187%	$268.8946	$268.89	$268.90	$268.90
Purchase #2	$133.45	13.170%	$151.0254	$151.03	$151.05	$151.00
Purchase #3	$157.29	5.451%	$165.8639	$165.86	$165.85	$165.90
Purchase #4	$42.39	7.211%	$45.4467	$45.45	$45.45	$45.40
Purchase #5	$155.51	8.537%	$168.7859	$168.79	$168.80	$168.80
Purchase #6	$87.78	5.448%	$92.5623	$92.56	$92.55	$92.60
Purchase #7	$169.98	13.203%	$192.4225	$192.42	$192.40	$192.40
7 purchase totals =	$988.24		$1,085.0013	$1,085.00	$1,085.00	$1,085.00