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	$67.76	9.638%	$74.2907	$74.29	$74.30	$74.30
Purchase #2	$69.80	9.250%	$76.2565	$76.26	$76.25	$76.30
Purchase #3	$50.28	5.588%	$53.0896	$53.09	$53.10	$53.10
Purchase #4	$214.52	10.680%	$237.4307	$237.43	$237.45	$237.40
Purchase #5	$6.72	6.394%	$7.1497	$7.15	$7.15	$7.10
Purchase #6	$166.47	3.575%	$172.4213	$172.42	$172.40	$172.40
Purchase #7	$145.91	4.777%	$152.8801	$152.88	$152.90	$152.90
7 purchase totals =	$721.46		$773.5186	$773.52	$773.55	$773.50