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	$76.43	8.412%	$82.8593	$82.86	$82.85	$82.90
Purchase #2	$34.35	10.572%	$37.9815	$37.98	$38.00	$38.00
Purchase #3	$118.89	6.345%	$126.4336	$126.43	$126.45	$126.40
Purchase #4	$170.50	5.268%	$179.4819	$179.48	$179.50	$179.50
Purchase #5	$160.88	13.513%	$182.6197	$182.62	$182.60	$182.60
Purchase #6	$150.90	12.318%	$169.4879	$169.49	$169.50	$169.50
Purchase #7	$16.28	12.512%	$18.317	$18.32	$18.30	$18.30
7 purchase totals =	$728.23		$797.1809	$797.18	$797.20	$797.20