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	$209.88	5.523%	$221.4717	$221.47	$221.45	$221.50
Purchase #2	$166.84	6.720%	$178.0516	$178.05	$178.05	$178.10
Purchase #3	$196.77	6.111%	$208.7946	$208.79	$208.80	$208.80
Purchase #4	$137.51	13.838%	$156.5386	$156.54	$156.55	$156.50
Purchase #5	$60.41	12.470%	$67.9431	$67.94	$67.95	$67.90
Purchase #6	$112.26	12.671%	$126.4845	$126.48	$126.50	$126.50
Purchase #7	$219.44	3.269%	$226.6135	$226.61	$226.60	$226.60
7 purchase totals =	$1,103.11		$1,185.8976	$1,185.88	$1,185.90	$1,185.90