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	$76.55	13.385%	$86.7962	$86.80	$86.80	$86.80
Purchase #2	$143.56	10.358%	$158.4299	$158.43	$158.45	$158.40
Purchase #3	$98.72	11.161%	$109.7381	$109.74	$109.75	$109.70
Purchase #4	$21.49	6.122%	$22.8056	$22.81	$22.80	$22.80
Purchase #5	$33.68	12.509%	$37.893	$37.89	$37.90	$37.90
Purchase #6	$178.62	12.215%	$200.4384	$200.44	$200.45	$200.40
Purchase #7	$92.38	9.321%	$100.9907	$100.99	$101.00	$101.00
7 purchase totals =	$645.00		$717.0919	$717.10	$717.15	$717.00