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	$52.60	13.448%	$59.6736	$59.67	$59.65	$59.70
Purchase #2	$111.39	5.704%	$117.7437	$117.74	$117.75	$117.70
Purchase #3	$192.57	3.857%	$199.9974	$200.00	$200.00	$200.00
Purchase #4	$181.83	10.385%	$200.713	$200.71	$200.70	$200.70
Purchase #5	$8.67	9.815%	$9.521	$9.52	$9.50	$9.50
Purchase #6	$118.48	8.776%	$128.8778	$128.88	$128.90	$128.90
Purchase #7	$164.32	12.802%	$185.3562	$185.36	$185.35	$185.40
7 purchase totals =	$829.86		$901.8827	$901.88	$901.85	$901.90