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	$153.64	3.153%	$158.4843	$158.48	$158.50	$158.50
Purchase #2	$35.98	11.684%	$40.1839	$40.18	$40.20	$40.20
Purchase #3	$126.58	9.321%	$138.3785	$138.38	$138.40	$138.40
Purchase #4	$112.86	11.741%	$126.1109	$126.11	$126.10	$126.10
Purchase #5	$140.27	13.259%	$158.8684	$158.87	$158.85	$158.90
Purchase #6	$205.73	9.690%	$225.6652	$225.67	$225.65	$225.70
Purchase #7	$168.51	5.872%	$178.4049	$178.40	$178.40	$178.40
7 purchase totals =	$943.57		$1,026.0961	$1,026.09	$1,026.10	$1,026.20