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	$40.39	13.361%	$45.7865	$45.79	$45.80	$45.80
Purchase #2	$66.32	10.756%	$73.4534	$73.45	$73.45	$73.50
Purchase #3	$69.26	11.856%	$77.4715	$77.47	$77.45	$77.50
Purchase #4	$199.71	12.328%	$224.3302	$224.33	$224.35	$224.30
Purchase #5	$129.55	12.129%	$145.2631	$145.26	$145.25	$145.30
Purchase #6	$164.28	6.546%	$175.0338	$175.03	$175.05	$175.00
Purchase #7	$95.42	5.726%	$100.8837	$100.88	$100.90	$100.90
7 purchase totals =	$764.93		$842.2222	$842.21	$842.25	$842.30