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	$169.46	13.771%	$192.7963	$192.80	$192.80	$192.80
Purchase #2	$18.51	5.559%	$19.539	$19.54	$19.55	$19.50
Purchase #3	$99.67	12.295%	$111.9244	$111.92	$111.90	$111.90
Purchase #4	$153.58	13.602%	$174.47	$174.47	$174.45	$174.50
Purchase #5	$11.40	3.490%	$11.7979	$11.80	$11.80	$11.80
Purchase #6	$221.33	9.552%	$242.4714	$242.47	$242.45	$242.50
Purchase #7	$92.86	11.124%	$103.1897	$103.19	$103.20	$103.20
7 purchase totals =	$766.81		$856.1887	$856.19	$856.15	$856.20