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	$124.70	5.233%	$131.2256	$131.23	$131.25	$131.20
Purchase #2	$161.41	7.104%	$172.8766	$172.88	$172.90	$172.90
Purchase #3	$145.41	7.733%	$156.6546	$156.65	$156.65	$156.70
Purchase #4	$38.50	13.320%	$43.6282	$43.63	$43.65	$43.60
Purchase #5	$137.41	11.311%	$152.9524	$152.95	$152.95	$153.00
Purchase #6	$13.96	10.223%	$15.3871	$15.39	$15.40	$15.40
Purchase #7	$234.52	4.413%	$244.8694	$244.87	$244.85	$244.90
7 purchase totals =	$855.91		$917.5939	$917.60	$917.65	$917.70