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	$168.96	9.676%	$185.3086	$185.31	$185.30	$185.30
Purchase #2	$9.92	13.750%	$11.284	$11.28	$11.30	$11.30
Purchase #3	$224.40	13.866%	$255.5153	$255.52	$255.50	$255.50
Purchase #4	$208.87	3.599%	$216.3872	$216.39	$216.40	$216.40
Purchase #5	$248.88	4.102%	$259.0891	$259.09	$259.10	$259.10
Purchase #6	$43.97	9.278%	$48.0495	$48.05	$48.05	$48.00
Purchase #7	$208.95	7.621%	$224.8741	$224.87	$224.85	$224.90
7 purchase totals =	$1,113.95		$1,200.5078	$1,200.51	$1,200.50	$1,200.50