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	$55.52	10.781%	$61.5056	$61.51	$61.50	$61.50
Purchase #2	$127.77	5.385%	$134.6504	$134.65	$134.65	$134.70
Purchase #3	$128.88	8.115%	$139.3386	$139.34	$139.35	$139.30
Purchase #4	$12.72	11.264%	$14.1528	$14.15	$14.15	$14.20
Purchase #5	$102.65	13.329%	$116.3322	$116.33	$116.35	$116.30
Purchase #6	$55.66	11.509%	$62.0659	$62.07	$62.05	$62.10
Purchase #7	$250.86	3.313%	$259.171	$259.17	$259.15	$259.20
7 purchase totals =	$734.06		$787.2165	$787.22	$787.20	$787.30