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	$224.56	9.745%	$246.4434	$246.44	$246.45	$246.40
Purchase #2	$213.78	11.592%	$238.5614	$238.56	$238.55	$238.60
Purchase #3	$215.35	6.151%	$228.5962	$228.60	$228.60	$228.60
Purchase #4	$214.68	8.847%	$233.6727	$233.67	$233.65	$233.70
Purchase #5	$162.27	13.689%	$184.4831	$184.48	$184.50	$184.50
Purchase #6	$74.38	12.184%	$83.4425	$83.44	$83.45	$83.40
Purchase #7	$34.34	10.261%	$37.8636	$37.86	$37.85	$37.90
7 purchase totals =	$1,139.36		$1,253.0629	$1,253.05	$1,253.05	$1,253.10