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	$116.93	8.623%	$127.0129	$127.01	$127.00	$127.00
Purchase #2	$98.26	5.284%	$103.4521	$103.45	$103.45	$103.50
Purchase #3	$202.55	8.266%	$219.2928	$219.29	$219.30	$219.30
Purchase #4	$43.43	7.254%	$46.5804	$46.58	$46.60	$46.60
Purchase #5	$23.35	6.709%	$24.9166	$24.92	$24.90	$24.90
Purchase #6	$90.91	4.407%	$94.9164	$94.92	$94.90	$94.90
Purchase #7	$174.72	9.397%	$191.1384	$191.14	$191.15	$191.10
7 purchase totals =	$750.15		$807.3096	$807.31	$807.30	$807.30