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	$243.89	6.208%	$259.0307	$259.03	$259.05	$259.00
Purchase #2	$150.72	7.227%	$161.6125	$161.61	$161.60	$161.60
Purchase #3	$92.75	13.402%	$105.1804	$105.18	$105.20	$105.20
Purchase #4	$182.68	12.511%	$205.5351	$205.54	$205.55	$205.50
Purchase #5	$104.58	11.373%	$116.4739	$116.47	$116.45	$116.50
Purchase #6	$92.35	7.798%	$99.5515	$99.55	$99.55	$99.60
Purchase #7	$130.45	5.703%	$137.8896	$137.89	$137.90	$137.90
7 purchase totals =	$997.42		$1,085.2737	$1,085.27	$1,085.30	$1,085.30