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	$98.89	12.687%	$111.4362	$111.44	$111.45	$111.40
Purchase #2	$38.99	4.581%	$40.7761	$40.78	$40.80	$40.80
Purchase #3	$137.35	10.290%	$151.4833	$151.48	$151.50	$151.50
Purchase #4	$198.28	8.350%	$214.8364	$214.84	$214.85	$214.80
Purchase #5	$230.30	8.170%	$249.1155	$249.12	$249.10	$249.10
Purchase #6	$19.69	6.680%	$21.0053	$21.01	$21.00	$21.00
Purchase #7	$225.94	3.684%	$234.2636	$234.26	$234.25	$234.30
7 purchase totals =	$949.44		$1,022.9164	$1,022.93	$1,022.95	$1,022.90