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	$215.94	11.643%	$241.0819	$241.08	$241.10	$241.10
Purchase #2	$17.89	9.798%	$19.6429	$19.64	$19.65	$19.60
Purchase #3	$99.98	11.496%	$111.4737	$111.47	$111.45	$111.50
Purchase #4	$226.54	4.638%	$237.0469	$237.05	$237.05	$237.00
Purchase #5	$54.71	9.150%	$59.716	$59.72	$59.70	$59.70
Purchase #6	$17.86	7.646%	$19.2256	$19.23	$19.25	$19.20
Purchase #7	$29.88	11.331%	$33.2657	$33.27	$33.25	$33.30
7 purchase totals =	$662.80		$721.4527	$721.46	$721.45	$721.40