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	$54.41	9.208%	$59.4201	$59.42	$59.40	$59.40
Purchase #2	$75.41	6.569%	$80.3637	$80.36	$80.35	$80.40
Purchase #3	$233.29	8.256%	$252.5504	$252.55	$252.55	$252.60
Purchase #4	$235.25	8.217%	$254.5805	$254.58	$254.60	$254.60
Purchase #5	$223.84	8.140%	$242.0606	$242.06	$242.05	$242.10
Purchase #6	$103.73	5.442%	$109.375	$109.38	$109.40	$109.40
Purchase #7	$13.30	9.203%	$14.524	$14.52	$14.50	$14.50
7 purchase totals =	$939.23		$1,012.8743	$1,012.87	$1,012.85	$1,013.00