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	$55.80	4.751%	$58.4511	$58.45	$58.45	$58.50
Purchase #2	$32.91	5.864%	$34.8398	$34.84	$34.85	$34.80
Purchase #3	$25.92	4.484%	$27.0823	$27.08	$27.10	$27.10
Purchase #4	$134.35	13.426%	$152.3878	$152.39	$152.40	$152.40
Purchase #5	$83.90	13.243%	$95.0109	$95.01	$95.00	$95.00
Purchase #6	$19.33	13.347%	$21.91	$21.91	$21.90	$21.90
Purchase #7	$131.77	11.281%	$146.635	$146.64	$146.65	$146.60
7 purchase totals =	$483.98		$536.3169	$536.32	$536.35	$536.30