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	$93.30	12.117%	$104.6052	$104.61	$104.60	$104.60
Purchase #2	$49.97	9.160%	$54.5473	$54.55	$54.55	$54.50
Purchase #3	$23.35	11.131%	$25.9491	$25.95	$25.95	$25.90
Purchase #4	$118.42	10.680%	$131.0673	$131.07	$131.05	$131.10
Purchase #5	$96.92	8.802%	$105.4509	$105.45	$105.45	$105.50
Purchase #6	$99.54	9.122%	$108.62	$108.62	$108.60	$108.60
Purchase #7	$240.30	7.304%	$257.8515	$257.85	$257.85	$257.90
7 purchase totals =	$721.80		$788.0913	$788.10	$788.05	$788.10