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	$130.59	8.428%	$141.5961	$141.60	$141.60	$141.60
Purchase #2	$25.75	5.263%	$27.1052	$27.11	$27.10	$27.10
Purchase #3	$230.39	8.304%	$249.5216	$249.52	$249.50	$249.50
Purchase #4	$190.30	11.699%	$212.5632	$212.56	$212.55	$212.60
Purchase #5	$64.94	9.396%	$71.0418	$71.04	$71.05	$71.00
Purchase #6	$99.83	11.275%	$111.0858	$111.09	$111.10	$111.10
Purchase #7	$34.78	13.497%	$39.4743	$39.47	$39.45	$39.50
7 purchase totals =	$776.58		$852.3880	$852.39	$852.35	$852.40