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	$244.63	4.387%	$255.3619	$255.36	$255.35	$255.40
Purchase #2	$157.92	9.804%	$173.4025	$173.40	$173.40	$173.40
Purchase #3	$130.78	4.553%	$136.7344	$136.73	$136.75	$136.70
Purchase #4	$196.38	10.321%	$216.6484	$216.65	$216.65	$216.60
Purchase #5	$152.94	7.732%	$164.7653	$164.77	$164.75	$164.80
Purchase #6	$109.61	6.759%	$117.0185	$117.02	$117.00	$117.00
Purchase #7	$143.76	10.282%	$158.5414	$158.54	$158.55	$158.50
7 purchase totals =	$1,136.02		$1,222.4724	$1,222.47	$1,222.45	$1,222.40