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	$100.64	7.646%	$108.3349	$108.33	$108.35	$108.30
Purchase #2	$219.59	9.209%	$239.812	$239.81	$239.80	$239.80
Purchase #3	$196.78	12.568%	$221.5113	$221.51	$221.50	$221.50
Purchase #4	$141.53	3.660%	$146.71	$146.71	$146.70	$146.70
Purchase #5	$219.52	6.247%	$233.2334	$233.23	$233.25	$233.20
Purchase #6	$42.36	3.294%	$43.7553	$43.76	$43.75	$43.80
Purchase #7	$38.98	8.737%	$42.3857	$42.39	$42.40	$42.40
7 purchase totals =	$959.40		$1,035.7426	$1,035.74	$1,035.75	$1,035.70