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	$108.69	5.668%	$114.8505	$114.85	$114.85	$114.90
Purchase #2	$241.89	12.245%	$271.5094	$271.51	$271.50	$271.50
Purchase #3	$91.65	8.836%	$99.7482	$99.75	$99.75	$99.70
Purchase #4	$15.54	6.586%	$16.5635	$16.56	$16.55	$16.60
Purchase #5	$68.67	8.652%	$74.6113	$74.61	$74.60	$74.60
Purchase #6	$43.26	4.170%	$45.0639	$45.06	$45.05	$45.10
Purchase #7	$83.85	5.522%	$88.4802	$88.48	$88.50	$88.50
7 purchase totals =	$653.55		$710.8270	$710.82	$710.80	$710.90