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	$218.98	7.646%	$235.7232	$235.72	$235.70	$235.70
Purchase #2	$183.99	8.106%	$198.9042	$198.90	$198.90	$198.90
Purchase #3	$99.29	12.702%	$111.9018	$111.90	$111.90	$111.90
Purchase #4	$182.67	5.183%	$192.1378	$192.14	$192.15	$192.10
Purchase #5	$12.76	7.646%	$13.7356	$13.74	$13.75	$13.70
Purchase #6	$237.46	7.598%	$255.5022	$255.50	$255.50	$255.50
Purchase #7	$66.86	6.442%	$71.1671	$71.17	$71.15	$71.20
7 purchase totals =	$1,002.01		$1,079.0719	$1,079.07	$1,079.05	$1,079.00