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	$168.76	13.847%	$192.1282	$192.13	$192.15	$192.10
Purchase #2	$94.84	4.731%	$99.3269	$99.33	$99.35	$99.30
Purchase #3	$143.28	7.382%	$153.8569	$153.86	$153.85	$153.90
Purchase #4	$239.85	4.246%	$250.034	$250.03	$250.05	$250.00
Purchase #5	$104.53	13.219%	$118.3478	$118.35	$118.35	$118.30
Purchase #6	$141.65	8.450%	$153.6194	$153.62	$153.60	$153.60
Purchase #7	$85.70	3.289%	$88.5187	$88.52	$88.50	$88.50
7 purchase totals =	$978.61		$1,055.8319	$1,055.84	$1,055.85	$1,055.70