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	$217.54	12.680%	$245.1241	$245.12	$245.10	$245.10
Purchase #2	$30.75	9.841%	$33.7761	$33.78	$33.80	$33.80
Purchase #3	$145.60	3.654%	$150.9202	$150.92	$150.90	$150.90
Purchase #4	$12.29	5.690%	$12.9893	$12.99	$13.00	$13.00
Purchase #5	$23.76	3.842%	$24.6729	$24.67	$24.65	$24.70
Purchase #6	$97.86	13.703%	$111.2698	$111.27	$111.25	$111.30
Purchase #7	$209.91	11.693%	$234.4548	$234.45	$234.45	$234.50
7 purchase totals =	$737.71		$813.2072	$813.20	$813.15	$813.30