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	$78.96	7.820%	$85.1347	$85.13	$85.15	$85.10
Purchase #2	$8.70	9.479%	$9.5247	$9.52	$9.50	$9.50
Purchase #3	$49.72	10.196%	$54.7895	$54.79	$54.80	$54.80
Purchase #4	$149.69	8.378%	$162.231	$162.23	$162.25	$162.20
Purchase #5	$152.57	13.267%	$172.8115	$172.81	$172.80	$172.80
Purchase #6	$233.29	10.754%	$258.378	$258.38	$258.40	$258.40
Purchase #7	$54.51	10.734%	$60.3611	$60.36	$60.35	$60.40
7 purchase totals =	$727.44		$803.2305	$803.22	$803.25	$803.20