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	$45.68	6.348%	$48.5798	$48.58	$48.60	$48.60
Purchase #2	$217.37	11.665%	$242.7262	$242.73	$242.75	$242.70
Purchase #3	$64.92	4.684%	$67.9609	$67.96	$67.95	$68.00
Purchase #4	$7.81	7.537%	$8.3986	$8.40	$8.40	$8.40
Purchase #5	$113.80	5.723%	$120.3128	$120.31	$120.30	$120.30
Purchase #6	$82.95	8.251%	$89.7942	$89.79	$89.80	$89.80
Purchase #7	$74.29	5.156%	$78.1204	$78.12	$78.10	$78.10
7 purchase totals =	$606.82		$655.8929	$655.89	$655.90	$655.90