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	$38.59	5.772%	$40.8174	$40.82	$40.80	$40.80
Purchase #2	$23.81	10.535%	$26.3184	$26.32	$26.30	$26.30
Purchase #3	$46.51	13.747%	$52.9037	$52.90	$52.90	$52.90
Purchase #4	$43.61	9.773%	$47.872	$47.87	$47.85	$47.90
Purchase #5	$16.67	9.649%	$18.2785	$18.28	$18.30	$18.30
Purchase #6	$99.35	6.397%	$105.7054	$105.71	$105.70	$105.70
Purchase #7	$134.34	7.691%	$144.6721	$144.67	$144.65	$144.70
7 purchase totals =	$402.88		$436.5675	$436.57	$436.50	$436.60