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	$155.39	13.151%	$175.8253	$175.83	$175.85	$175.80
Purchase #2	$172.83	10.653%	$191.2416	$191.24	$191.25	$191.20
Purchase #3	$40.75	4.156%	$42.4436	$42.44	$42.45	$42.40
Purchase #4	$21.35	5.382%	$22.4991	$22.50	$22.50	$22.50
Purchase #5	$181.57	10.614%	$200.8418	$200.84	$200.85	$200.80
Purchase #6	$67.88	10.189%	$74.7963	$74.80	$74.80	$74.80
Purchase #7	$225.77	8.171%	$244.2177	$244.22	$244.20	$244.20
7 purchase totals =	$865.54		$951.8654	$951.87	$951.90	$951.70