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	$45.91	13.762%	$52.2281	$52.23	$52.25	$52.20
Purchase #2	$71.65	12.214%	$80.4013	$80.40	$80.40	$80.40
Purchase #3	$153.47	5.769%	$162.3237	$162.32	$162.30	$162.30
Purchase #4	$106.76	4.385%	$111.4414	$111.44	$111.45	$111.40
Purchase #5	$74.92	4.203%	$78.0689	$78.07	$78.05	$78.10
Purchase #6	$162.73	8.420%	$176.4319	$176.43	$176.45	$176.40
Purchase #7	$38.66	12.572%	$43.5203	$43.52	$43.50	$43.50
7 purchase totals =	$654.10		$704.4156	$704.41	$704.40	$704.30