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	$106.39	9.336%	$116.3226	$116.32	$116.30	$116.30
Purchase #2	$194.49	9.681%	$213.3186	$213.32	$213.30	$213.30
Purchase #3	$222.29	6.680%	$237.139	$237.14	$237.15	$237.10
Purchase #4	$152.31	13.493%	$172.8612	$172.86	$172.85	$172.90
Purchase #5	$41.42	8.767%	$45.0513	$45.05	$45.05	$45.10
Purchase #6	$145.25	3.367%	$150.1406	$150.14	$150.15	$150.10
Purchase #7	$157.32	7.657%	$169.366	$169.37	$169.35	$169.40
7 purchase totals =	$1,019.47		$1,104.1993	$1,104.20	$1,104.15	$1,104.20