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	$233.45	3.493%	$241.6044	$241.60	$241.60	$241.60
Purchase #2	$147.81	5.437%	$155.8464	$155.85	$155.85	$155.80
Purchase #3	$63.34	3.732%	$65.7038	$65.70	$65.70	$65.70
Purchase #4	$42.31	9.422%	$46.2964	$46.30	$46.30	$46.30
Purchase #5	$17.70	6.606%	$18.8693	$18.87	$18.85	$18.90
Purchase #6	$55.57	8.735%	$60.424	$60.42	$60.40	$60.40
Purchase #7	$207.30	11.735%	$231.6267	$231.63	$231.65	$231.60
7 purchase totals =	$767.48		$820.3710	$820.37	$820.35	$820.30