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	3.859%	$104.5237	$104.52	$104.50	$104.50
Purchase #2	$207.66	3.704%	$215.3517	$215.35	$215.35	$215.40
Purchase #3	$126.34	3.272%	$130.4738	$130.47	$130.45	$130.50
Purchase #4	$124.76	10.163%	$137.4394	$137.44	$137.45	$137.40
Purchase #5	$111.61	10.815%	$123.6806	$123.68	$123.70	$123.70
Purchase #6	$34.71	6.766%	$37.0585	$37.06	$37.05	$37.10
Purchase #7	$13.70	9.296%	$14.9736	$14.97	$14.95	$15.00
7 purchase totals =	$719.42		$763.5013	$763.49	$763.45	$763.60