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	$183.86	8.307%	$199.1333	$199.13	$199.15	$199.10
Purchase #2	$164.67	4.777%	$172.5363	$172.54	$172.55	$172.50
Purchase #3	$176.74	6.314%	$187.8994	$187.90	$187.90	$187.90
Purchase #4	$52.92	12.777%	$59.6816	$59.68	$59.70	$59.70
Purchase #5	$105.89	13.312%	$119.9861	$119.99	$120.00	$120.00
Purchase #6	$173.98	9.709%	$190.8717	$190.87	$190.85	$190.90
Purchase #7	$152.61	10.489%	$168.6173	$168.62	$168.60	$168.60
7 purchase totals =	$1,010.67		$1,098.7257	$1,098.73	$1,098.75	$1,098.70