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	$133.61	7.265%	$143.3168	$143.32	$143.30	$143.30
Purchase #2	$14.59	8.676%	$15.8558	$15.86	$15.85	$15.90
Purchase #3	$111.46	5.434%	$117.5167	$117.52	$117.50	$117.50
Purchase #4	$223.26	6.357%	$237.4526	$237.45	$237.45	$237.50
Purchase #5	$107.98	10.225%	$119.021	$119.02	$119.00	$119.00
Purchase #6	$95.33	10.377%	$105.2224	$105.22	$105.20	$105.20
Purchase #7	$54.36	6.381%	$57.8287	$57.83	$57.85	$57.80
7 purchase totals =	$740.59		$796.2140	$796.22	$796.15	$796.20