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	$130.60	11.268%	$145.316	$145.32	$145.30	$145.30
Purchase #2	$172.43	11.586%	$192.4077	$192.41	$192.40	$192.40
Purchase #3	$132.57	6.666%	$141.4071	$141.41	$141.40	$141.40
Purchase #4	$63.94	12.278%	$71.7906	$71.79	$71.80	$71.80
Purchase #5	$112.31	7.795%	$121.0646	$121.06	$121.05	$121.10
Purchase #6	$18.53	10.743%	$20.5207	$20.52	$20.50	$20.50
Purchase #7	$127.47	12.242%	$143.0749	$143.07	$143.05	$143.10
7 purchase totals =	$757.85		$835.5816	$835.58	$835.50	$835.60