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	$104.43	6.106%	$110.8065	$110.81	$110.80	$110.80
Purchase #2	$158.49	5.601%	$167.367	$167.37	$167.35	$167.40
Purchase #3	$149.91	4.236%	$156.2602	$156.26	$156.25	$156.30
Purchase #4	$132.99	10.144%	$146.4805	$146.48	$146.50	$146.50
Purchase #5	$206.27	7.699%	$222.1507	$222.15	$222.15	$222.20
Purchase #6	$68.93	6.314%	$73.2822	$73.28	$73.30	$73.30
Purchase #7	$247.28	10.187%	$272.4704	$272.47	$272.45	$272.50
7 purchase totals =	$1,068.30		$1,148.8175	$1,148.82	$1,148.80	$1,149.00