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	$125.38	4.543%	$131.076	$131.08	$131.10	$131.10
Purchase #2	$10.71	5.218%	$11.2688	$11.27	$11.25	$11.30
Purchase #3	$93.54	5.685%	$98.8577	$98.86	$98.85	$98.90
Purchase #4	$89.39	10.455%	$98.7357	$98.74	$98.75	$98.70
Purchase #5	$54.59	3.408%	$56.4504	$56.45	$56.45	$56.50
Purchase #6	$19.45	4.867%	$20.3966	$20.40	$20.40	$20.40
Purchase #7	$226.30	11.704%	$252.7862	$252.79	$252.80	$252.80
7 purchase totals =	$619.36		$669.5714	$669.59	$669.60	$669.70