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	$109.54	3.128%	$112.9664	$112.97	$112.95	$113.00
Purchase #2	$166.32	3.239%	$171.7071	$171.71	$171.70	$171.70
Purchase #3	$153.28	5.281%	$161.3747	$161.37	$161.35	$161.40
Purchase #4	$68.82	3.282%	$71.0787	$71.08	$71.10	$71.10
Purchase #5	$196.37	4.590%	$205.3834	$205.38	$205.40	$205.40
Purchase #6	$83.27	4.635%	$87.1296	$87.13	$87.15	$87.10
Purchase #7	$104.26	5.299%	$109.7847	$109.78	$109.80	$109.80
7 purchase totals =	$881.86		$919.4246	$919.42	$919.45	$919.50