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	$227.38	5.573%	$240.0519	$240.05	$240.05	$240.10
Purchase #2	$245.56	4.834%	$257.4304	$257.43	$257.45	$257.40
Purchase #3	$119.52	10.825%	$132.458	$132.46	$132.45	$132.50
Purchase #4	$173.89	4.532%	$181.7707	$181.77	$181.75	$181.80
Purchase #5	$183.89	12.648%	$207.1484	$207.15	$207.15	$207.10
Purchase #6	$20.59	5.756%	$21.7752	$21.78	$21.80	$21.80
Purchase #7	$159.89	5.381%	$168.4937	$168.49	$168.50	$168.50
7 purchase totals =	$1,130.72		$1,209.1283	$1,209.13	$1,209.15	$1,209.20