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	$128.30	11.274%	$142.7645	$142.76	$142.75	$142.80
Purchase #2	$118.83	3.370%	$122.8346	$122.83	$122.85	$122.80
Purchase #3	$115.54	13.318%	$130.9276	$130.93	$130.95	$130.90
Purchase #4	$119.51	3.651%	$123.8733	$123.87	$123.85	$123.90
Purchase #5	$231.86	9.335%	$253.5041	$253.50	$253.50	$253.50
Purchase #6	$188.88	11.838%	$211.2396	$211.24	$211.25	$211.20
Purchase #7	$206.30	12.185%	$231.4377	$231.44	$231.45	$231.40
7 purchase totals =	$1,109.22		$1,216.5814	$1,216.57	$1,216.60	$1,216.50