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	$124.33	7.191%	$133.2706	$133.27	$133.25	$133.30
Purchase #2	$114.58	4.224%	$119.4199	$119.42	$119.40	$119.40
Purchase #3	$213.93	12.824%	$241.3644	$241.36	$241.35	$241.40
Purchase #4	$74.36	4.872%	$77.9828	$77.98	$78.00	$78.00
Purchase #5	$213.25	6.534%	$227.1838	$227.18	$227.20	$227.20
Purchase #6	$149.33	3.190%	$154.0936	$154.09	$154.10	$154.10
Purchase #7	$80.50	11.209%	$89.5232	$89.52	$89.50	$89.50
7 purchase totals =	$970.28		$1,042.8383	$1,042.82	$1,042.80	$1,042.90