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	$211.32	9.380%	$231.1418	$231.14	$231.15	$231.10
Purchase #2	$80.35	12.381%	$90.2981	$90.30	$90.30	$90.30
Purchase #3	$104.41	7.570%	$112.3138	$112.31	$112.30	$112.30
Purchase #4	$136.29	11.227%	$151.5913	$151.59	$151.60	$151.60
Purchase #5	$203.30	7.205%	$217.9478	$217.95	$217.95	$217.90
Purchase #6	$65.32	6.692%	$69.6912	$69.69	$69.70	$69.70
Purchase #7	$44.73	4.738%	$46.8493	$46.85	$46.85	$46.80
7 purchase totals =	$845.72		$919.8333	$919.83	$919.85	$919.70