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	$208.67	6.697%	$222.6446	$222.64	$222.65	$222.60
Purchase #2	$205.26	8.379%	$222.4587	$222.46	$222.45	$222.50
Purchase #3	$173.27	6.607%	$184.7179	$184.72	$184.70	$184.70
Purchase #4	$81.47	13.271%	$92.2819	$92.28	$92.30	$92.30
Purchase #5	$70.48	7.155%	$75.5228	$75.52	$75.50	$75.50
Purchase #6	$15.81	9.241%	$17.271	$17.27	$17.25	$17.30
Purchase #7	$241.85	6.791%	$258.274	$258.27	$258.25	$258.30
7 purchase totals =	$996.81		$1,073.1709	$1,073.16	$1,073.10	$1,073.20