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	$32.59	6.209%	$34.6135	$34.61	$34.60	$34.60
Purchase #2	$71.25	6.118%	$75.6091	$75.61	$75.60	$75.60
Purchase #3	$241.78	12.497%	$271.9952	$272.00	$272.00	$272.00
Purchase #4	$70.28	3.276%	$72.5824	$72.58	$72.60	$72.60
Purchase #5	$44.61	13.327%	$50.5552	$50.56	$50.55	$50.60
Purchase #6	$196.28	11.488%	$218.8286	$218.83	$218.85	$218.80
Purchase #7	$145.85	8.427%	$158.1408	$158.14	$158.15	$158.10
7 purchase totals =	$802.64		$882.3248	$882.33	$882.35	$882.30