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	$163.34	9.572%	$178.9749	$178.97	$178.95	$179.00
Purchase #2	$113.74	8.863%	$123.8208	$123.82	$123.80	$123.80
Purchase #3	$66.65	6.361%	$70.8896	$70.89	$70.90	$70.90
Purchase #4	$206.62	10.261%	$227.8213	$227.82	$227.80	$227.80
Purchase #5	$179.69	6.171%	$190.7787	$190.78	$190.80	$190.80
Purchase #6	$9.56	13.600%	$10.8602	$10.86	$10.85	$10.90
Purchase #7	$178.81	8.670%	$194.3128	$194.31	$194.30	$194.30
7 purchase totals =	$918.41		$997.4583	$997.45	$997.40	$997.50