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	$86.26	4.557%	$90.1909	$90.19	$90.20	$90.20
Purchase #2	$183.88	9.187%	$200.7731	$200.77	$200.75	$200.80
Purchase #3	$192.31	13.664%	$218.5872	$218.59	$218.60	$218.60
Purchase #4	$233.66	6.195%	$248.1352	$248.14	$248.15	$248.10
Purchase #5	$213.72	5.561%	$225.605	$225.61	$225.60	$225.60
Purchase #6	$222.42	3.506%	$230.218	$230.22	$230.20	$230.20
Purchase #7	$95.25	6.149%	$101.1069	$101.11	$101.10	$101.10
7 purchase totals =	$1,227.50		$1,314.6163	$1,314.63	$1,314.60	$1,314.60