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	$54.41	5.182%	$57.2295	$57.23	$57.25	$57.20
Purchase #2	$194.94	6.467%	$207.5468	$207.55	$207.55	$207.50
Purchase #3	$163.45	13.111%	$184.8799	$184.88	$184.90	$184.90
Purchase #4	$35.52	8.698%	$38.6095	$38.61	$38.60	$38.60
Purchase #5	$145.92	5.110%	$153.3765	$153.38	$153.40	$153.40
Purchase #6	$235.47	4.195%	$245.348	$245.35	$245.35	$245.30
Purchase #7	$192.83	13.366%	$218.6037	$218.60	$218.60	$218.60
7 purchase totals =	$1,022.54		$1,105.5939	$1,105.60	$1,105.65	$1,105.50