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	$107.68	3.622%	$111.5802	$111.58	$111.60	$111.60
Purchase #2	$218.75	13.621%	$248.5459	$248.55	$248.55	$248.50
Purchase #3	$243.79	5.582%	$257.3984	$257.40	$257.40	$257.40
Purchase #4	$174.92	12.276%	$196.3932	$196.39	$196.40	$196.40
Purchase #5	$98.72	11.638%	$110.209	$110.21	$110.20	$110.20
Purchase #6	$113.61	13.149%	$128.5486	$128.55	$128.55	$128.50
Purchase #7	$154.45	12.198%	$173.2898	$173.29	$173.30	$173.30
7 purchase totals =	$1,111.92		$1,225.9651	$1,225.97	$1,226.00	$1,225.90