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	$205.73	8.173%	$222.5443	$222.54	$222.55	$222.50
Purchase #2	$85.83	9.705%	$94.1598	$94.16	$94.15	$94.20
Purchase #3	$96.45	3.596%	$99.9183	$99.92	$99.90	$99.90
Purchase #4	$240.57	13.456%	$272.9411	$272.94	$272.95	$272.90
Purchase #5	$63.26	7.711%	$68.138	$68.14	$68.15	$68.10
Purchase #6	$47.93	11.704%	$53.5397	$53.54	$53.55	$53.50
Purchase #7	$56.60	10.133%	$62.3353	$62.34	$62.35	$62.30
7 purchase totals =	$796.37		$873.5765	$873.58	$873.60	$873.40