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	$217.78	4.687%	$227.9873	$227.99	$228.00	$228.00
Purchase #2	$169.75	5.209%	$178.5923	$178.59	$178.60	$178.60
Purchase #3	$62.85	12.773%	$70.8778	$70.88	$70.90	$70.90
Purchase #4	$151.79	8.210%	$164.252	$164.25	$164.25	$164.30
Purchase #5	$201.76	9.660%	$221.25	$221.25	$221.25	$221.30
Purchase #6	$79.40	7.783%	$85.5797	$85.58	$85.60	$85.60
Purchase #7	$119.87	10.419%	$132.3593	$132.36	$132.35	$132.40
7 purchase totals =	$1,003.20		$1,080.8984	$1,080.90	$1,080.95	$1,081.10