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	$46.74	3.780%	$48.5068	$48.51	$48.50	$48.50
Purchase #2	$70.93	7.258%	$76.0781	$76.08	$76.10	$76.10
Purchase #3	$10.72	4.611%	$11.2143	$11.21	$11.20	$11.20
Purchase #4	$166.84	7.178%	$178.8158	$178.82	$178.80	$178.80
Purchase #5	$167.49	7.154%	$179.4722	$179.47	$179.45	$179.50
Purchase #6	$213.47	13.257%	$241.7697	$241.77	$241.75	$241.80
Purchase #7	$65.81	10.315%	$72.5983	$72.60	$72.60	$72.60
7 purchase totals =	$742.00		$808.4552	$808.46	$808.40	$808.50