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	$60.62	5.122%	$63.725	$63.73	$63.75	$63.70
Purchase #2	$190.74	3.232%	$196.9047	$196.90	$196.90	$196.90
Purchase #3	$105.57	11.856%	$118.0864	$118.09	$118.10	$118.10
Purchase #4	$95.61	5.120%	$100.5052	$100.51	$100.50	$100.50
Purchase #5	$213.31	9.328%	$233.2076	$233.21	$233.20	$233.20
Purchase #6	$159.74	12.718%	$180.0557	$180.06	$180.05	$180.10
Purchase #7	$137.84	13.530%	$156.4898	$156.49	$156.50	$156.50
7 purchase totals =	$963.43		$1,048.9744	$1,048.99	$1,049.00	$1,049.00