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	$45.25	3.693%	$46.9211	$46.92	$46.90	$46.90
Purchase #2	$194.80	13.626%	$221.3434	$221.34	$221.35	$221.30
Purchase #3	$70.43	10.671%	$77.9456	$77.95	$77.95	$77.90
Purchase #4	$73.88	10.337%	$81.517	$81.52	$81.50	$81.50
Purchase #5	$38.60	5.562%	$40.7469	$40.75	$40.75	$40.70
Purchase #6	$223.55	8.660%	$242.9094	$242.91	$242.90	$242.90
Purchase #7	$93.51	12.786%	$105.4662	$105.47	$105.45	$105.50
7 purchase totals =	$740.02		$816.8496	$816.86	$816.80	$816.70