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	$69.54	10.105%	$76.567	$76.57	$76.55	$76.60
Purchase #2	$54.85	13.440%	$62.2218	$62.22	$62.20	$62.20
Purchase #3	$105.53	7.514%	$113.4595	$113.46	$113.45	$113.50
Purchase #4	$46.41	12.367%	$52.1495	$52.15	$52.15	$52.10
Purchase #5	$63.58	13.658%	$72.2638	$72.26	$72.25	$72.30
Purchase #6	$66.83	5.644%	$70.6019	$70.60	$70.60	$70.60
Purchase #7	$49.39	4.864%	$51.7923	$51.79	$51.80	$51.80
7 purchase totals =	$456.13		$499.0558	$499.05	$499.00	$499.10