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	$18.43	3.516%	$19.078	$19.08	$19.10	$19.10
Purchase #2	$41.47	12.195%	$46.5273	$46.53	$46.55	$46.50
Purchase #3	$103.63	9.196%	$113.1598	$113.16	$113.15	$113.20
Purchase #4	$50.32	4.820%	$52.7454	$52.75	$52.75	$52.70
Purchase #5	$150.77	10.447%	$166.5209	$166.52	$166.50	$166.50
Purchase #6	$122.57	3.519%	$126.8832	$126.88	$126.90	$126.90
Purchase #7	$99.95	11.661%	$111.6052	$111.61	$111.60	$111.60
7 purchase totals =	$587.14		$636.5198	$636.53	$636.55	$636.50