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	$141.85	9.640%	$155.5243	$155.52	$155.50	$155.50
Purchase #2	$199.92	9.499%	$218.9104	$218.91	$218.90	$218.90
Purchase #3	$48.32	3.773%	$50.1431	$50.14	$50.15	$50.10
Purchase #4	$226.59	5.250%	$238.486	$238.49	$238.50	$238.50
Purchase #5	$16.99	6.390%	$18.0757	$18.08	$18.10	$18.10
Purchase #6	$82.93	7.234%	$88.9292	$88.93	$88.95	$88.90
Purchase #7	$169.98	13.259%	$192.5176	$192.52	$192.50	$192.50
7 purchase totals =	$886.58		$962.5863	$962.59	$962.60	$962.50