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	$52.42	9.832%	$57.5739	$57.57	$57.55	$57.60
Purchase #2	$142.36	12.283%	$159.8461	$159.85	$159.85	$159.80
Purchase #3	$54.25	13.419%	$61.5298	$61.53	$61.55	$61.50
Purchase #4	$65.59	10.490%	$72.4704	$72.47	$72.45	$72.50
Purchase #5	$36.66	5.137%	$38.5432	$38.54	$38.55	$38.50
Purchase #6	$55.32	10.567%	$61.1657	$61.17	$61.15	$61.20
Purchase #7	$206.61	5.102%	$217.1512	$217.15	$217.15	$217.20
7 purchase totals =	$613.21		$668.2803	$668.28	$668.25	$668.30