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	$174.66	7.777%	$188.2433	$188.24	$188.25	$188.20
Purchase #2	$105.61	6.604%	$112.5845	$112.58	$112.60	$112.60
Purchase #3	$157.47	5.652%	$166.3702	$166.37	$166.35	$166.40
Purchase #4	$89.66	13.122%	$101.4252	$101.43	$101.45	$101.40
Purchase #5	$12.48	8.241%	$13.5085	$13.51	$13.50	$13.50
Purchase #6	$131.38	9.230%	$143.5064	$143.51	$143.50	$143.50
Purchase #7	$16.55	12.579%	$18.6318	$18.63	$18.65	$18.60
7 purchase totals =	$687.81		$744.2699	$744.27	$744.30	$744.20