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	$153.27	5.615%	$161.8761	$161.88	$161.90	$161.90
Purchase #2	$234.40	13.120%	$265.1533	$265.15	$265.15	$265.20
Purchase #3	$91.29	12.416%	$102.6246	$102.62	$102.60	$102.60
Purchase #4	$190.54	4.411%	$198.9447	$198.94	$198.95	$198.90
Purchase #5	$151.99	5.104%	$159.7476	$159.75	$159.75	$159.70
Purchase #6	$152.31	13.620%	$173.0546	$173.05	$173.05	$173.10
Purchase #7	$82.55	7.852%	$89.0318	$89.03	$89.05	$89.00
7 purchase totals =	$1,056.35		$1,150.4327	$1,150.42	$1,150.45	$1,150.40