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	$204.41	10.515%	$225.9037	$225.90	$225.90	$225.90
Purchase #2	$172.83	4.615%	$180.8061	$180.81	$180.80	$180.80
Purchase #3	$228.74	12.593%	$257.5452	$257.55	$257.55	$257.50
Purchase #4	$115.52	12.675%	$130.1622	$130.16	$130.15	$130.20
Purchase #5	$154.25	10.727%	$170.7964	$170.80	$170.80	$170.80
Purchase #6	$85.38	5.505%	$90.0802	$90.08	$90.10	$90.10
Purchase #7	$85.80	12.613%	$96.622	$96.62	$96.60	$96.60
7 purchase totals =	$1,046.93		$1,151.9158	$1,151.92	$1,151.90	$1,151.90