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	$62.65	4.816%	$65.6672	$65.67	$65.65	$65.70
Purchase #2	$54.64	9.873%	$60.0346	$60.03	$60.05	$60.00
Purchase #3	$111.62	10.351%	$123.1738	$123.17	$123.15	$123.20
Purchase #4	$126.52	3.729%	$131.2379	$131.24	$131.25	$131.20
Purchase #5	$99.67	8.773%	$108.414	$108.41	$108.40	$108.40
Purchase #6	$174.89	8.248%	$189.3149	$189.31	$189.30	$189.30
Purchase #7	$164.38	9.816%	$180.5155	$180.52	$180.50	$180.50
7 purchase totals =	$794.37		$858.3579	$858.35	$858.30	$858.30