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	$247.29	7.580%	$266.0346	$266.03	$266.05	$266.00
Purchase #2	$85.44	4.475%	$89.2634	$89.26	$89.25	$89.30
Purchase #3	$196.64	6.296%	$209.0205	$209.02	$209.00	$209.00
Purchase #4	$166.44	12.447%	$187.1568	$187.16	$187.15	$187.20
Purchase #5	$91.70	9.643%	$100.5426	$100.54	$100.55	$100.50
Purchase #6	$219.43	5.485%	$231.4657	$231.47	$231.45	$231.50
Purchase #7	$215.91	13.381%	$244.8009	$244.80	$244.80	$244.80
7 purchase totals =	$1,222.85		$1,328.2845	$1,328.28	$1,328.25	$1,328.30