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	$206.70	10.619%	$228.6495	$228.65	$228.65	$228.60
Purchase #2	$159.91	7.839%	$172.4453	$172.45	$172.45	$172.40
Purchase #3	$184.86	4.200%	$192.6241	$192.62	$192.60	$192.60
Purchase #4	$25.73	6.555%	$27.4166	$27.42	$27.40	$27.40
Purchase #5	$32.38	9.672%	$35.5118	$35.51	$35.50	$35.50
Purchase #6	$83.84	7.449%	$90.0852	$90.09	$90.10	$90.10
Purchase #7	$239.59	7.483%	$257.5185	$257.52	$257.50	$257.50
7 purchase totals =	$933.01		$1,004.2510	$1,004.26	$1,004.20	$1,004.10