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	$158.55	9.662%	$173.8691	$173.87	$173.85	$173.90
Purchase #2	$107.58	9.759%	$118.0787	$118.08	$118.10	$118.10
Purchase #3	$208.62	3.528%	$215.9801	$215.98	$216.00	$216.00
Purchase #4	$74.70	5.138%	$78.5381	$78.54	$78.55	$78.50
Purchase #5	$89.92	11.247%	$100.0333	$100.03	$100.05	$100.00
Purchase #6	$41.77	4.260%	$43.5494	$43.55	$43.55	$43.50
Purchase #7	$53.38	3.319%	$55.1517	$55.15	$55.15	$55.20
7 purchase totals =	$734.52		$785.2004	$785.20	$785.25	$785.20