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	$183.57	8.868%	$199.849	$199.85	$199.85	$199.80
Purchase #2	$74.87	4.593%	$78.3088	$78.31	$78.30	$78.30
Purchase #3	$160.78	12.782%	$181.3309	$181.33	$181.35	$181.30
Purchase #4	$41.60	9.201%	$45.4276	$45.43	$45.45	$45.40
Purchase #5	$170.72	5.533%	$180.1659	$180.17	$180.15	$180.20
Purchase #6	$134.40	9.249%	$146.8307	$146.83	$146.85	$146.80
Purchase #7	$81.73	10.677%	$90.4563	$90.46	$90.45	$90.50
7 purchase totals =	$847.67		$922.3692	$922.38	$922.40	$922.30