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	$117.36	4.327%	$122.4382	$122.44	$122.45	$122.40
Purchase #2	$239.78	3.700%	$248.6519	$248.65	$248.65	$248.70
Purchase #3	$92.99	12.563%	$104.6723	$104.67	$104.65	$104.70
Purchase #4	$55.87	6.179%	$59.3222	$59.32	$59.30	$59.30
Purchase #5	$100.91	11.213%	$112.225	$112.23	$112.25	$112.20
Purchase #6	$146.80	7.725%	$158.1403	$158.14	$158.15	$158.10
Purchase #7	$84.83	5.675%	$89.6441	$89.64	$89.65	$89.60
7 purchase totals =	$838.54		$895.0940	$895.09	$895.10	$895.00