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	$186.77	11.774%	$208.7603	$208.76	$208.75	$208.80
Purchase #2	$191.87	6.754%	$204.8289	$204.83	$204.85	$204.80
Purchase #3	$173.69	8.624%	$188.669	$188.67	$188.65	$188.70
Purchase #4	$103.25	13.794%	$117.4923	$117.49	$117.50	$117.50
Purchase #5	$215.62	13.181%	$244.0409	$244.04	$244.05	$244.00
Purchase #6	$243.87	4.660%	$255.2343	$255.23	$255.25	$255.20
Purchase #7	$81.52	4.695%	$85.3474	$85.35	$85.35	$85.30
7 purchase totals =	$1,196.59		$1,304.3731	$1,304.37	$1,304.40	$1,304.30