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	$29.42	9.762%	$32.292	$32.29	$32.30	$32.30
Purchase #2	$128.52	12.626%	$144.7469	$144.75	$144.75	$144.70
Purchase #3	$62.96	5.536%	$66.4455	$66.45	$66.45	$66.40
Purchase #4	$72.85	12.496%	$81.9533	$81.95	$81.95	$82.00
Purchase #5	$241.66	3.513%	$250.1495	$250.15	$250.15	$250.10
Purchase #6	$205.95	5.488%	$217.2525	$217.25	$217.25	$217.30
Purchase #7	$250.37	5.434%	$263.9751	$263.98	$264.00	$264.00
7 purchase totals =	$991.73		$1,056.8148	$1,056.82	$1,056.85	$1,056.80