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	$225.89	12.280%	$253.6293	$253.63	$253.65	$253.60
Purchase #2	$126.54	11.799%	$141.4705	$141.47	$141.45	$141.50
Purchase #3	$198.95	12.554%	$223.9262	$223.93	$223.95	$223.90
Purchase #4	$105.96	13.408%	$120.1671	$120.17	$120.15	$120.20
Purchase #5	$26.39	5.416%	$27.8193	$27.82	$27.80	$27.80
Purchase #6	$127.35	4.122%	$132.5994	$132.60	$132.60	$132.60
Purchase #7	$200.58	11.813%	$224.2745	$224.27	$224.25	$224.30
7 purchase totals =	$1,011.66		$1,123.8863	$1,123.89	$1,123.85	$1,123.90