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	$187.93	9.175%	$205.1726	$205.17	$205.15	$205.20
Purchase #2	$44.83	13.126%	$50.7144	$50.71	$50.70	$50.70
Purchase #3	$131.85	8.495%	$143.0507	$143.05	$143.05	$143.10
Purchase #4	$233.65	4.691%	$244.6105	$244.61	$244.60	$244.60
Purchase #5	$116.95	12.816%	$131.9383	$131.94	$131.95	$131.90
Purchase #6	$104.40	10.623%	$115.4904	$115.49	$115.50	$115.50
Purchase #7	$199.93	11.324%	$222.5701	$222.57	$222.55	$222.60
7 purchase totals =	$1,019.54		$1,113.5470	$1,113.54	$1,113.50	$1,113.60