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	$40.87	13.409%	$46.3503	$46.35	$46.35	$46.40
Purchase #2	$72.67	13.799%	$82.6977	$82.70	$82.70	$82.70
Purchase #3	$87.50	5.422%	$92.2443	$92.24	$92.25	$92.20
Purchase #4	$56.81	4.135%	$59.1591	$59.16	$59.15	$59.20
Purchase #5	$98.71	12.752%	$111.2975	$111.30	$111.30	$111.30
Purchase #6	$37.57	10.734%	$41.6028	$41.60	$41.60	$41.60
Purchase #7	$60.49	6.416%	$64.371	$64.37	$64.35	$64.40
7 purchase totals =	$454.62		$497.7227	$497.72	$497.70	$497.80