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	$235.37	8.487%	$255.3459	$255.35	$255.35	$255.30
Purchase #2	$247.57	9.638%	$271.4308	$271.43	$271.45	$271.40
Purchase #3	$247.82	7.430%	$266.233	$266.23	$266.25	$266.20
Purchase #4	$127.87	10.741%	$141.6045	$141.60	$141.60	$141.60
Purchase #5	$91.88	9.286%	$100.412	$100.41	$100.40	$100.40
Purchase #6	$76.76	6.792%	$81.9735	$81.97	$81.95	$82.00
Purchase #7	$137.54	5.633%	$145.2876	$145.29	$145.30	$145.30
7 purchase totals =	$1,164.81		$1,262.2873	$1,262.28	$1,262.30	$1,262.20