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	$112.86	12.850%	$127.3625	$127.36	$127.35	$127.40
Purchase #2	$227.73	4.198%	$237.2901	$237.29	$237.30	$237.30
Purchase #3	$214.89	10.485%	$237.4212	$237.42	$237.40	$237.40
Purchase #4	$49.95	7.225%	$53.5589	$53.56	$53.55	$53.60
Purchase #5	$60.36	9.437%	$66.0562	$66.06	$66.05	$66.10
Purchase #6	$174.30	8.665%	$189.4031	$189.40	$189.40	$189.40
Purchase #7	$139.54	10.802%	$154.6131	$154.61	$154.60	$154.60
7 purchase totals =	$979.63		$1,065.7051	$1,065.70	$1,065.65	$1,065.80