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	$118.54	7.718%	$127.6889	$127.69	$127.70	$127.70
Purchase #2	$141.56	5.864%	$149.8611	$149.86	$149.85	$149.90
Purchase #3	$71.30	7.462%	$76.6204	$76.62	$76.60	$76.60
Purchase #4	$105.86	12.652%	$119.2534	$119.25	$119.25	$119.30
Purchase #5	$100.72	4.841%	$105.5959	$105.60	$105.60	$105.60
Purchase #6	$58.50	13.298%	$66.2793	$66.28	$66.30	$66.30
Purchase #7	$225.76	3.871%	$234.4992	$234.50	$234.50	$234.50
7 purchase totals =	$822.24		$879.7982	$879.80	$879.80	$879.90