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	$142.75	10.770%	$158.1242	$158.12	$158.10	$158.10
Purchase #2	$111.30	10.855%	$123.3816	$123.38	$123.40	$123.40
Purchase #3	$208.69	10.404%	$230.4021	$230.40	$230.40	$230.40
Purchase #4	$239.39	7.332%	$256.9421	$256.94	$256.95	$256.90
Purchase #5	$178.90	10.226%	$197.1943	$197.19	$197.20	$197.20
Purchase #6	$184.81	10.468%	$204.1559	$204.16	$204.15	$204.20
Purchase #7	$247.75	3.279%	$255.8737	$255.87	$255.85	$255.90
7 purchase totals =	$1,313.59		$1,426.0739	$1,426.06	$1,426.05	$1,426.10