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	$62.86	10.712%	$69.5936	$69.59	$69.60	$69.60
Purchase #2	$150.38	10.806%	$166.6301	$166.63	$166.65	$166.60
Purchase #3	$153.42	11.127%	$170.491	$170.49	$170.50	$170.50
Purchase #4	$218.79	7.609%	$235.4377	$235.44	$235.45	$235.40
Purchase #5	$199.25	11.820%	$222.8014	$222.80	$222.80	$222.80
Purchase #6	$134.34	12.235%	$150.7765	$150.78	$150.80	$150.80
Purchase #7	$138.72	5.762%	$146.713	$146.71	$146.70	$146.70
7 purchase totals =	$1,057.76		$1,162.4433	$1,162.44	$1,162.50	$1,162.40