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	$36.36	11.124%	$40.4047	$40.40	$40.40	$40.40
Purchase #2	$11.48	8.680%	$12.4765	$12.48	$12.50	$12.50
Purchase #3	$87.73	13.103%	$99.2253	$99.23	$99.25	$99.20
Purchase #4	$54.98	4.284%	$57.3353	$57.34	$57.35	$57.30
Purchase #5	$52.81	6.498%	$56.2416	$56.24	$56.25	$56.20
Purchase #6	$100.45	7.836%	$108.3213	$108.32	$108.30	$108.30
Purchase #7	$86.48	6.388%	$92.0043	$92.00	$92.00	$92.00
7 purchase totals =	$430.29		$466.0090	$466.01	$466.05	$465.90