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	$237.56	7.411%	$255.1656	$255.17	$255.15	$255.20
Purchase #2	$205.86	6.638%	$219.525	$219.53	$219.55	$219.50
Purchase #3	$101.79	4.139%	$106.0031	$106.00	$106.00	$106.00
Purchase #4	$137.52	11.498%	$153.332	$153.33	$153.35	$153.30
Purchase #5	$95.40	8.392%	$103.406	$103.41	$103.40	$103.40
Purchase #6	$164.91	13.603%	$187.3427	$187.34	$187.35	$187.30
Purchase #7	$44.86	3.403%	$46.3866	$46.39	$46.40	$46.40
7 purchase totals =	$987.90		$1,071.1610	$1,071.17	$1,071.20	$1,071.10