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	$111.81	10.566%	$123.6238	$123.62	$123.60	$123.60
Purchase #2	$227.48	9.452%	$248.9814	$248.98	$249.00	$249.00
Purchase #3	$212.52	13.349%	$240.8893	$240.89	$240.90	$240.90
Purchase #4	$117.40	9.810%	$128.9169	$128.92	$128.90	$128.90
Purchase #5	$30.31	10.563%	$33.5116	$33.51	$33.50	$33.50
Purchase #6	$194.38	10.404%	$214.6033	$214.60	$214.60	$214.60
Purchase #7	$13.43	8.532%	$14.5758	$14.58	$14.60	$14.60
7 purchase totals =	$907.33		$1,005.1021	$1,005.10	$1,005.10	$1,005.10