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	$50.31	13.526%	$57.1149	$57.11	$57.10	$57.10
Purchase #2	$152.55	5.249%	$160.5573	$160.56	$160.55	$160.60
Purchase #3	$125.37	7.433%	$134.6888	$134.69	$134.70	$134.70
Purchase #4	$181.87	10.228%	$200.4717	$200.47	$200.45	$200.50
Purchase #5	$117.51	9.310%	$128.4502	$128.45	$128.45	$128.50
Purchase #6	$114.35	4.284%	$119.2488	$119.25	$119.25	$119.20
Purchase #7	$188.28	12.641%	$212.0805	$212.08	$212.10	$212.10
7 purchase totals =	$930.24		$1,012.6122	$1,012.61	$1,012.60	$1,012.70