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	$242.64	10.830%	$268.9179	$268.92	$268.90	$268.90
Purchase #2	$247.98	12.244%	$278.3427	$278.34	$278.35	$278.30
Purchase #3	$188.53	6.573%	$200.9221	$200.92	$200.90	$200.90
Purchase #4	$231.25	12.786%	$260.8176	$260.82	$260.80	$260.80
Purchase #5	$13.35	7.169%	$14.3071	$14.31	$14.30	$14.30
Purchase #6	$152.71	5.152%	$160.5776	$160.58	$160.60	$160.60
Purchase #7	$48.88	10.806%	$54.162	$54.16	$54.15	$54.20
7 purchase totals =	$1,125.34		$1,238.0470	$1,238.05	$1,238.00	$1,238.00