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	$20.86	6.440%	$22.2034	$22.20	$22.20	$22.20
Purchase #2	$88.69	5.426%	$93.5023	$93.50	$93.50	$93.50
Purchase #3	$127.85	10.581%	$141.3778	$141.38	$141.40	$141.40
Purchase #4	$134.37	9.778%	$147.5087	$147.51	$147.50	$147.50
Purchase #5	$234.52	12.189%	$263.1056	$263.11	$263.10	$263.10
Purchase #6	$27.63	13.548%	$31.3733	$31.37	$31.35	$31.40
Purchase #7	$33.64	3.501%	$34.8177	$34.82	$34.80	$34.80
7 purchase totals =	$667.56		$733.8888	$733.89	$733.85	$733.90