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	$88.53	3.435%	$91.571	$91.57	$91.55	$91.60
Purchase #2	$9.53	6.604%	$10.1594	$10.16	$10.15	$10.20
Purchase #3	$65.71	10.285%	$72.4683	$72.47	$72.45	$72.50
Purchase #4	$103.37	7.566%	$111.191	$111.19	$111.20	$111.20
Purchase #5	$217.75	10.868%	$241.4151	$241.42	$241.40	$241.40
Purchase #6	$25.57	10.340%	$28.2139	$28.21	$28.20	$28.20
Purchase #7	$209.56	8.353%	$227.0645	$227.06	$227.05	$227.10
7 purchase totals =	$720.02		$782.0832	$782.08	$782.00	$782.20