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	$59.42	13.638%	$67.5237	$67.52	$67.50	$67.50
Purchase #2	$221.98	3.282%	$229.2654	$229.27	$229.25	$229.30
Purchase #3	$190.68	13.780%	$216.9557	$216.96	$216.95	$217.00
Purchase #4	$71.40	5.528%	$75.347	$75.35	$75.35	$75.30
Purchase #5	$230.35	6.114%	$244.4336	$244.43	$244.45	$244.40
Purchase #6	$199.54	12.566%	$224.6142	$224.61	$224.60	$224.60
Purchase #7	$103.96	4.741%	$108.8887	$108.89	$108.90	$108.90
7 purchase totals =	$1,077.33		$1,167.0283	$1,167.03	$1,167.00	$1,167.00