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	$59.52	13.427%	$67.5118	$67.51	$67.50	$67.50
Purchase #2	$171.68	6.367%	$182.6109	$182.61	$182.60	$182.60
Purchase #3	$74.50	4.572%	$77.9061	$77.91	$77.90	$77.90
Purchase #4	$167.45	9.251%	$182.9408	$182.94	$182.95	$182.90
Purchase #5	$234.30	9.217%	$255.8954	$255.90	$255.90	$255.90
Purchase #6	$204.40	11.179%	$227.2499	$227.25	$227.25	$227.20
Purchase #7	$207.79	4.804%	$217.7722	$217.77	$217.75	$217.80
7 purchase totals =	$1,119.64		$1,211.8871	$1,211.89	$1,211.85	$1,211.80