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	$87.61	9.394%	$95.8401	$95.84	$95.85	$95.80
Purchase #2	$66.87	8.196%	$72.3507	$72.35	$72.35	$72.40
Purchase #3	$36.32	4.723%	$38.0354	$38.04	$38.05	$38.00
Purchase #4	$58.74	7.679%	$63.2506	$63.25	$63.25	$63.30
Purchase #5	$136.89	10.647%	$151.4647	$151.46	$151.45	$151.50
Purchase #6	$46.79	13.150%	$52.9429	$52.94	$52.95	$52.90
Purchase #7	$247.41	8.423%	$268.2493	$268.25	$268.25	$268.20
7 purchase totals =	$680.63		$742.1337	$742.13	$742.15	$742.10