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	$149.64	11.574%	$166.9593	$166.96	$166.95	$167.00
Purchase #2	$145.28	11.147%	$161.4744	$161.47	$161.45	$161.50
Purchase #3	$173.70	4.556%	$181.6138	$181.61	$181.60	$181.60
Purchase #4	$166.76	5.264%	$175.5382	$175.54	$175.55	$175.50
Purchase #5	$161.31	3.795%	$167.4317	$167.43	$167.45	$167.40
Purchase #6	$92.32	9.140%	$100.758	$100.76	$100.75	$100.80
Purchase #7	$241.75	5.699%	$255.5273	$255.53	$255.55	$255.50
7 purchase totals =	$1,130.76		$1,209.3027	$1,209.30	$1,209.30	$1,209.30