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	$113.97	5.811%	$120.5928	$120.59	$120.60	$120.60
Purchase #2	$158.39	12.439%	$178.0921	$178.09	$178.10	$178.10
Purchase #3	$113.88	4.408%	$118.8998	$118.90	$118.90	$118.90
Purchase #4	$112.47	13.198%	$127.3138	$127.31	$127.30	$127.30
Purchase #5	$223.64	11.570%	$249.5151	$249.52	$249.50	$249.50
Purchase #6	$113.43	3.795%	$117.7347	$117.73	$117.75	$117.70
Purchase #7	$23.56	3.789%	$24.4527	$24.45	$24.45	$24.50
7 purchase totals =	$859.34		$936.6010	$936.59	$936.60	$936.60