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	$177.32	4.623%	$185.5175	$185.52	$185.50	$185.50
Purchase #2	$177.59	12.531%	$199.8438	$199.84	$199.85	$199.80
Purchase #3	$63.77	10.211%	$70.2816	$70.28	$70.30	$70.30
Purchase #4	$68.83	6.594%	$73.3687	$73.37	$73.35	$73.40
Purchase #5	$81.86	8.838%	$89.0948	$89.09	$89.10	$89.10
Purchase #6	$143.29	7.742%	$154.3835	$154.38	$154.40	$154.40
Purchase #7	$230.79	13.861%	$262.7798	$262.78	$262.80	$262.80
7 purchase totals =	$943.45		$1,035.2697	$1,035.26	$1,035.30	$1,035.30