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	$117.77	8.194%	$127.4201	$127.42	$127.40	$127.40
Purchase #2	$179.56	7.792%	$193.5513	$193.55	$193.55	$193.60
Purchase #3	$124.61	13.345%	$141.2392	$141.24	$141.25	$141.20
Purchase #4	$166.97	12.418%	$187.7043	$187.70	$187.70	$187.70
Purchase #5	$54.32	9.634%	$59.5532	$59.55	$59.55	$59.60
Purchase #6	$27.51	3.133%	$28.3719	$28.37	$28.35	$28.40
Purchase #7	$215.97	10.403%	$238.4374	$238.44	$238.45	$238.40
7 purchase totals =	$886.71		$976.2774	$976.27	$976.25	$976.30