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	$67.42	7.448%	$72.4414	$72.44	$72.45	$72.40
Purchase #2	$115.94	13.724%	$131.8516	$131.85	$131.85	$131.90
Purchase #3	$124.82	4.345%	$130.2434	$130.24	$130.25	$130.20
Purchase #4	$114.35	3.442%	$118.2859	$118.29	$118.30	$118.30
Purchase #5	$18.91	11.822%	$21.1455	$21.15	$21.15	$21.10
Purchase #6	$231.32	3.842%	$240.2073	$240.21	$240.20	$240.20
Purchase #7	$141.55	8.321%	$153.3284	$153.33	$153.35	$153.30
7 purchase totals =	$814.31		$867.5035	$867.51	$867.55	$867.40