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	$250.90	3.553%	$259.8145	$259.81	$259.80	$259.80
Purchase #2	$13.94	5.525%	$14.7102	$14.71	$14.70	$14.70
Purchase #3	$161.89	11.115%	$179.8841	$179.88	$179.90	$179.90
Purchase #4	$199.82	11.126%	$222.052	$222.05	$222.05	$222.10
Purchase #5	$100.41	8.203%	$108.6466	$108.65	$108.65	$108.60
Purchase #6	$153.61	9.734%	$168.5624	$168.56	$168.55	$168.60
Purchase #7	$168.65	10.244%	$185.9265	$185.93	$185.95	$185.90
7 purchase totals =	$1,049.22		$1,139.5963	$1,139.59	$1,139.60	$1,139.60