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	$212.35	12.204%	$238.2652	$238.27	$238.25	$238.30
Purchase #2	$152.91	6.319%	$162.5724	$162.57	$162.55	$162.60
Purchase #3	$9.67	11.382%	$10.7706	$10.77	$10.75	$10.80
Purchase #4	$13.91	3.614%	$14.4127	$14.41	$14.40	$14.40
Purchase #5	$91.70	3.602%	$95.003	$95.00	$95.00	$95.00
Purchase #6	$90.69	9.583%	$99.3808	$99.38	$99.40	$99.40
Purchase #7	$144.78	6.781%	$154.5975	$154.60	$154.60	$154.60
7 purchase totals =	$716.01		$775.0022	$775.00	$774.95	$775.10