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	$240.62	8.447%	$260.9452	$260.95	$260.95	$260.90
Purchase #2	$64.76	6.327%	$68.8574	$68.86	$68.85	$68.90
Purchase #3	$140.80	3.601%	$145.8702	$145.87	$145.85	$145.90
Purchase #4	$72.59	10.719%	$80.3709	$80.37	$80.35	$80.40
Purchase #5	$111.52	10.532%	$123.2653	$123.27	$123.25	$123.30
Purchase #6	$232.72	8.840%	$253.2924	$253.29	$253.30	$253.30
Purchase #7	$182.47	10.103%	$200.9049	$200.90	$200.90	$200.90
7 purchase totals =	$1,045.48		$1,133.5063	$1,133.51	$1,133.45	$1,133.60