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	$225.85	9.474%	$247.247	$247.25	$247.25	$247.20
Purchase #2	$136.77	5.478%	$144.2623	$144.26	$144.25	$144.30
Purchase #3	$151.68	5.863%	$160.573	$160.57	$160.55	$160.60
Purchase #4	$172.63	9.342%	$188.7571	$188.76	$188.75	$188.80
Purchase #5	$103.93	13.587%	$118.051	$118.05	$118.05	$118.10
Purchase #6	$82.54	9.333%	$90.2435	$90.24	$90.25	$90.20
Purchase #7	$197.31	10.520%	$218.067	$218.07	$218.05	$218.10
7 purchase totals =	$1,070.71		$1,167.2009	$1,167.20	$1,167.15	$1,167.30