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	$174.56	5.563%	$184.2708	$184.27	$184.25	$184.30
Purchase #2	$99.27	7.117%	$106.335	$106.34	$106.35	$106.30
Purchase #3	$240.39	4.154%	$250.3758	$250.38	$250.40	$250.40
Purchase #4	$177.87	9.212%	$194.2554	$194.26	$194.25	$194.30
Purchase #5	$148.91	4.473%	$155.5707	$155.57	$155.55	$155.60
Purchase #6	$11.63	8.382%	$12.6048	$12.60	$12.60	$12.60
Purchase #7	$59.47	11.856%	$66.5208	$66.52	$66.50	$66.50
7 purchase totals =	$912.10		$969.9333	$969.94	$969.90	$970.00