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	$148.28	5.784%	$156.8565	$156.86	$156.85	$156.90
Purchase #2	$55.43	4.638%	$58.0008	$58.00	$58.00	$58.00
Purchase #3	$71.76	9.261%	$78.4057	$78.41	$78.40	$78.40
Purchase #4	$119.40	3.808%	$123.9468	$123.95	$123.95	$123.90
Purchase #5	$184.35	6.521%	$196.3715	$196.37	$196.35	$196.40
Purchase #6	$111.64	8.610%	$121.2522	$121.25	$121.25	$121.30
Purchase #7	$12.57	7.155%	$13.4694	$13.47	$13.45	$13.50
7 purchase totals =	$703.43		$748.3029	$748.31	$748.25	$748.40