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	$238.84	11.133%	$265.4301	$265.43	$265.45	$265.40
Purchase #2	$211.78	7.465%	$227.5894	$227.59	$227.60	$227.60
Purchase #3	$233.85	10.499%	$258.4019	$258.40	$258.40	$258.40
Purchase #4	$70.47	10.753%	$78.0476	$78.05	$78.05	$78.00
Purchase #5	$176.75	11.158%	$196.4718	$196.47	$196.45	$196.50
Purchase #6	$220.54	7.643%	$237.3959	$237.40	$237.40	$237.40
Purchase #7	$181.82	7.522%	$195.4965	$195.50	$195.50	$195.50
7 purchase totals =	$1,334.05		$1,458.8332	$1,458.84	$1,458.85	$1,458.80