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	$133.27	11.692%	$148.8519	$148.85	$148.85	$148.90
Purchase #2	$87.50	4.679%	$91.5941	$91.59	$91.60	$91.60
Purchase #3	$62.83	12.241%	$70.521	$70.52	$70.50	$70.50
Purchase #4	$147.58	5.861%	$156.2297	$156.23	$156.25	$156.20
Purchase #5	$34.38	11.499%	$38.3334	$38.33	$38.35	$38.30
Purchase #6	$10.89	13.863%	$12.3997	$12.40	$12.40	$12.40
Purchase #7	$211.72	11.738%	$236.5717	$236.57	$236.55	$236.60
7 purchase totals =	$688.17		$754.5015	$754.49	$754.50	$754.50