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	$205.82	8.320%	$222.9442	$222.94	$222.95	$222.90
Purchase #2	$132.70	7.501%	$142.6538	$142.65	$142.65	$142.70
Purchase #3	$90.30	4.379%	$94.2542	$94.25	$94.25	$94.30
Purchase #4	$147.38	9.184%	$160.9154	$160.92	$160.90	$160.90
Purchase #5	$204.39	9.188%	$223.1694	$223.17	$223.15	$223.20
Purchase #6	$137.34	10.510%	$151.7744	$151.77	$151.75	$151.80
Purchase #7	$212.35	13.788%	$241.6288	$241.63	$241.65	$241.60
7 purchase totals =	$1,130.28		$1,237.3402	$1,237.33	$1,237.30	$1,237.40