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	$232.86	3.434%	$240.8564	$240.86	$240.85	$240.90
Purchase #2	$82.85	7.660%	$89.1963	$89.20	$89.20	$89.20
Purchase #3	$40.31	8.328%	$43.667	$43.67	$43.65	$43.70
Purchase #4	$43.60	4.373%	$45.5066	$45.51	$45.50	$45.50
Purchase #5	$101.27	10.843%	$112.2507	$112.25	$112.25	$112.30
Purchase #6	$21.45	6.702%	$22.8876	$22.89	$22.90	$22.90
Purchase #7	$212.70	3.161%	$219.4234	$219.42	$219.40	$219.40
7 purchase totals =	$735.04		$773.7880	$773.80	$773.75	$773.90