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	$219.43	13.475%	$248.9982	$249.00	$249.00	$249.00
Purchase #2	$164.68	4.175%	$171.5554	$171.56	$171.55	$171.60
Purchase #3	$79.61	13.475%	$90.3374	$90.34	$90.35	$90.30
Purchase #4	$210.63	12.521%	$237.003	$237.00	$237.00	$237.00
Purchase #5	$67.40	4.371%	$70.3461	$70.35	$70.35	$70.30
Purchase #6	$106.61	9.406%	$116.6377	$116.64	$116.65	$116.60
Purchase #7	$152.60	5.170%	$160.4894	$160.49	$160.50	$160.50
7 purchase totals =	$1,000.96		$1,095.3672	$1,095.38	$1,095.40	$1,095.30