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	$47.87	10.208%	$52.7566	$52.76	$52.75	$52.80
Purchase #2	$172.89	3.675%	$179.2437	$179.24	$179.25	$179.20
Purchase #3	$94.47	4.549%	$98.7674	$98.77	$98.75	$98.80
Purchase #4	$37.38	3.302%	$38.6143	$38.61	$38.60	$38.60
Purchase #5	$173.28	6.544%	$184.6194	$184.62	$184.60	$184.60
Purchase #6	$169.94	7.201%	$182.1774	$182.18	$182.20	$182.20
Purchase #7	$100.79	12.569%	$113.4583	$113.46	$113.45	$113.50
7 purchase totals =	$796.62		$849.6371	$849.64	$849.60	$849.70