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	$206.42	6.253%	$219.3274	$219.33	$219.35	$219.30
Purchase #2	$241.78	5.837%	$255.8927	$255.89	$255.90	$255.90
Purchase #3	$241.70	5.190%	$254.2442	$254.24	$254.25	$254.20
Purchase #4	$40.85	7.503%	$43.915	$43.92	$43.90	$43.90
Purchase #5	$211.33	5.776%	$223.5364	$223.54	$223.55	$223.50
Purchase #6	$138.33	10.210%	$152.4535	$152.45	$152.45	$152.50
Purchase #7	$38.52	12.219%	$43.2268	$43.23	$43.25	$43.20
7 purchase totals =	$1,118.93		$1,192.5960	$1,192.60	$1,192.65	$1,192.50