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	$244.83	9.200%	$267.3544	$267.35	$267.35	$267.40
Purchase #2	$53.41	11.219%	$59.4021	$59.40	$59.40	$59.40
Purchase #3	$144.38	8.591%	$156.7837	$156.78	$156.80	$156.80
Purchase #4	$53.34	7.165%	$57.1618	$57.16	$57.15	$57.20
Purchase #5	$66.82	11.340%	$74.3974	$74.40	$74.40	$74.40
Purchase #6	$116.90	9.548%	$128.0616	$128.06	$128.05	$128.10
Purchase #7	$154.55	8.441%	$167.5956	$167.60	$167.60	$167.60
7 purchase totals =	$834.23		$910.7566	$910.75	$910.75	$910.90