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	$79.59	10.131%	$87.6533	$87.65	$87.65	$87.70
Purchase #2	$235.50	12.160%	$264.1368	$264.14	$264.15	$264.10
Purchase #3	$29.41	13.748%	$33.4533	$33.45	$33.45	$33.50
Purchase #4	$19.55	4.510%	$20.4317	$20.43	$20.45	$20.40
Purchase #5	$176.56	5.428%	$186.1437	$186.14	$186.15	$186.10
Purchase #6	$184.64	10.197%	$203.4677	$203.47	$203.45	$203.50
Purchase #7	$210.57	6.521%	$224.3013	$224.30	$224.30	$224.30
7 purchase totals =	$935.82		$1,019.5878	$1,019.58	$1,019.60	$1,019.60