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	$40.73	13.325%	$46.1573	$46.16	$46.15	$46.20
Purchase #2	$70.66	13.869%	$80.4598	$80.46	$80.45	$80.50
Purchase #3	$37.42	7.320%	$40.1591	$40.16	$40.15	$40.20
Purchase #4	$148.49	13.559%	$168.6238	$168.62	$168.60	$168.60
Purchase #5	$146.97	13.241%	$166.4303	$166.43	$166.45	$166.40
Purchase #6	$14.29	6.762%	$15.2563	$15.26	$15.25	$15.30
Purchase #7	$173.60	12.511%	$195.3191	$195.32	$195.30	$195.30
7 purchase totals =	$632.16		$712.4057	$712.41	$712.35	$712.50