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	$52.48	3.593%	$54.3656	$54.37	$54.35	$54.40
Purchase #2	$67.27	11.223%	$74.8197	$74.82	$74.80	$74.80
Purchase #3	$90.91	10.638%	$100.581	$100.58	$100.60	$100.60
Purchase #4	$166.70	10.597%	$184.3652	$184.37	$184.35	$184.40
Purchase #5	$38.69	4.282%	$40.3467	$40.35	$40.35	$40.30
Purchase #6	$205.77	3.470%	$212.9102	$212.91	$212.90	$212.90
Purchase #7	$132.80	4.556%	$138.8504	$138.85	$138.85	$138.90
7 purchase totals =	$754.62		$806.2388	$806.25	$806.20	$806.30