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	$16.57	10.188%	$18.2582	$18.26	$18.25	$18.30
Purchase #2	$47.61	10.472%	$52.5957	$52.60	$52.60	$52.60
Purchase #3	$189.30	8.481%	$205.3545	$205.35	$205.35	$205.40
Purchase #4	$183.51	3.750%	$190.3916	$190.39	$190.40	$190.40
Purchase #5	$94.87	5.817%	$100.3886	$100.39	$100.40	$100.40
Purchase #6	$184.90	10.391%	$204.113	$204.11	$204.10	$204.10
Purchase #7	$221.58	13.285%	$251.0169	$251.02	$251.00	$251.00
7 purchase totals =	$938.34		$1,022.1185	$1,022.12	$1,022.10	$1,022.20