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	$61.80	8.296%	$66.9269	$66.93	$66.95	$66.90
Purchase #2	$124.64	10.320%	$137.5028	$137.50	$137.50	$137.50
Purchase #3	$49.39	10.557%	$54.6041	$54.60	$54.60	$54.60
Purchase #4	$231.80	9.788%	$254.4886	$254.49	$254.50	$254.50
Purchase #5	$61.25	10.189%	$67.4908	$67.49	$67.50	$67.50
Purchase #6	$239.82	4.205%	$249.9044	$249.90	$249.90	$249.90
Purchase #7	$76.59	11.518%	$85.4116	$85.41	$85.40	$85.40
7 purchase totals =	$845.29		$916.3292	$916.32	$916.35	$916.30