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	$138.59	7.247%	$148.6336	$148.63	$148.65	$148.60
Purchase #2	$106.63	4.419%	$111.342	$111.34	$111.35	$111.30
Purchase #3	$49.80	6.467%	$53.0206	$53.02	$53.00	$53.00
Purchase #4	$87.59	8.836%	$95.3295	$95.33	$95.35	$95.30
Purchase #5	$106.37	5.311%	$112.0193	$112.02	$112.00	$112.00
Purchase #6	$197.97	6.390%	$210.6203	$210.62	$210.60	$210.60
Purchase #7	$211.52	4.761%	$221.5905	$221.59	$221.60	$221.60
7 purchase totals =	$898.47		$952.5558	$952.55	$952.55	$952.40