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	$32.48	12.707%	$36.6072	$36.61	$36.60	$36.60
Purchase #2	$54.25	13.716%	$61.6909	$61.69	$61.70	$61.70
Purchase #3	$72.57	7.167%	$77.7711	$77.77	$77.75	$77.80
Purchase #4	$52.80	4.557%	$55.2061	$55.21	$55.20	$55.20
Purchase #5	$9.34	11.591%	$10.4226	$10.42	$10.40	$10.40
Purchase #6	$33.91	10.115%	$37.34	$37.34	$37.35	$37.30
Purchase #7	$167.87	8.103%	$181.4725	$181.47	$181.45	$181.50
7 purchase totals =	$423.22		$460.5104	$460.51	$460.45	$460.50