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	$32.33	7.714%	$34.8239	$34.82	$34.80	$34.80
Purchase #2	$118.48	7.700%	$127.603	$127.60	$127.60	$127.60
Purchase #3	$206.49	8.565%	$224.1759	$224.18	$224.20	$224.20
Purchase #4	$10.91	7.423%	$11.7198	$11.72	$11.70	$11.70
Purchase #5	$121.31	12.440%	$136.401	$136.40	$136.40	$136.40
Purchase #6	$113.26	8.857%	$123.2914	$123.29	$123.30	$123.30
Purchase #7	$6.43	12.733%	$7.2487	$7.25	$7.25	$7.20
7 purchase totals =	$609.21		$665.2637	$665.26	$665.25	$665.20