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	$86.71	9.710%	$95.1295	$95.13	$95.15	$95.10
Purchase #2	$116.45	9.588%	$127.6152	$127.62	$127.60	$127.60
Purchase #3	$161.40	9.184%	$176.223	$176.22	$176.20	$176.20
Purchase #4	$180.80	10.836%	$200.3915	$200.39	$200.40	$200.40
Purchase #5	$83.80	6.604%	$89.3342	$89.33	$89.35	$89.30
Purchase #6	$53.72	10.444%	$59.3305	$59.33	$59.35	$59.30
Purchase #7	$214.50	9.631%	$235.1585	$235.16	$235.15	$235.20
7 purchase totals =	$897.38		$983.1824	$983.18	$983.20	$983.10