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	$36.82	11.798%	$41.164	$41.16	$41.15	$41.20
Purchase #2	$63.51	13.278%	$71.9429	$71.94	$71.95	$71.90
Purchase #3	$192.95	12.169%	$216.4301	$216.43	$216.45	$216.40
Purchase #4	$155.49	6.800%	$166.0633	$166.06	$166.05	$166.10
Purchase #5	$42.37	3.460%	$43.836	$43.84	$43.85	$43.80
Purchase #6	$145.90	8.849%	$158.8107	$158.81	$158.80	$158.80
Purchase #7	$225.41	3.595%	$233.5135	$233.51	$233.50	$233.50
7 purchase totals =	$862.45		$931.7605	$931.75	$931.75	$931.70