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	$43.77	11.319%	$48.7243	$48.72	$48.70	$48.70
Purchase #2	$50.79	5.268%	$53.4656	$53.47	$53.45	$53.50
Purchase #3	$5.86	6.772%	$6.2568	$6.26	$6.25	$6.30
Purchase #4	$78.80	4.727%	$82.5249	$82.52	$82.50	$82.50
Purchase #5	$207.60	7.403%	$222.9686	$222.97	$222.95	$223.00
Purchase #6	$159.28	10.662%	$176.2624	$176.26	$176.25	$176.30
Purchase #7	$58.47	11.621%	$65.2648	$65.26	$65.25	$65.30
7 purchase totals =	$604.57		$655.4674	$655.46	$655.35	$655.60