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	$77.31	10.458%	$85.3951	$85.40	$85.40	$85.40
Purchase #2	$37.83	4.667%	$39.5955	$39.60	$39.60	$39.60
Purchase #3	$169.45	13.140%	$191.7157	$191.72	$191.70	$191.70
Purchase #4	$34.90	3.772%	$36.2164	$36.22	$36.20	$36.20
Purchase #5	$211.52	4.516%	$221.0722	$221.07	$221.05	$221.10
Purchase #6	$69.66	3.630%	$72.1887	$72.19	$72.20	$72.20
Purchase #7	$196.62	10.714%	$217.6859	$217.69	$217.70	$217.70
7 purchase totals =	$797.29		$863.8695	$863.89	$863.85	$863.90