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	$168.45	13.152%	$190.6045	$190.60	$190.60	$190.60
Purchase #2	$242.82	6.462%	$258.511	$258.51	$258.50	$258.50
Purchase #3	$116.70	10.179%	$128.5789	$128.58	$128.60	$128.60
Purchase #4	$131.60	7.137%	$140.9923	$140.99	$141.00	$141.00
Purchase #5	$159.54	7.809%	$171.9985	$172.00	$172.00	$172.00
Purchase #6	$82.59	12.527%	$92.936	$92.94	$92.95	$92.90
Purchase #7	$9.65	9.158%	$10.5337	$10.53	$10.55	$10.50
7 purchase totals =	$911.35		$994.1549	$994.15	$994.20	$994.10