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	$61.36	10.693%	$67.9212	$67.92	$67.90	$67.90
Purchase #2	$195.46	10.730%	$216.4329	$216.43	$216.45	$216.40
Purchase #3	$230.67	8.323%	$249.8687	$249.87	$249.85	$249.90
Purchase #4	$176.44	8.134%	$190.7916	$190.79	$190.80	$190.80
Purchase #5	$225.52	10.667%	$249.5762	$249.58	$249.60	$249.60
Purchase #6	$50.44	7.837%	$54.393	$54.39	$54.40	$54.40
Purchase #7	$48.38	8.762%	$52.6191	$52.62	$52.60	$52.60
7 purchase totals =	$988.27		$1,081.6027	$1,081.60	$1,081.60	$1,081.60