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	$11.69	13.660%	$13.2869	$13.29	$13.30	$13.30
Purchase #2	$136.67	11.383%	$152.2271	$152.23	$152.25	$152.20
Purchase #3	$198.61	12.136%	$222.7133	$222.71	$222.70	$222.70
Purchase #4	$240.63	10.848%	$266.7335	$266.73	$266.75	$266.70
Purchase #5	$103.92	6.814%	$111.0011	$111.00	$111.00	$111.00
Purchase #6	$208.66	9.550%	$228.587	$228.59	$228.60	$228.60
Purchase #7	$22.27	12.239%	$24.9956	$25.00	$25.00	$25.00
7 purchase totals =	$922.45		$1,019.5445	$1,019.55	$1,019.60	$1,019.50