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	$104.72	10.865%	$116.0978	$116.10	$116.10	$116.10
Purchase #2	$70.96	3.150%	$73.1952	$73.20	$73.20	$73.20
Purchase #3	$50.73	7.587%	$54.5789	$54.58	$54.60	$54.60
Purchase #4	$72.66	9.136%	$79.2982	$79.30	$79.30	$79.30
Purchase #5	$198.45	4.872%	$208.1185	$208.12	$208.10	$208.10
Purchase #6	$59.56	13.863%	$67.8168	$67.82	$67.80	$67.80
Purchase #7	$109.30	7.438%	$117.4297	$117.43	$117.45	$117.40
7 purchase totals =	$666.38		$716.5351	$716.55	$716.55	$716.50