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	$128.71	10.594%	$142.3455	$142.35	$142.35	$142.30
Purchase #2	$168.50	7.506%	$181.1476	$181.15	$181.15	$181.10
Purchase #3	$228.71	13.324%	$259.1833	$259.18	$259.20	$259.20
Purchase #4	$163.75	5.777%	$173.2098	$173.21	$173.20	$173.20
Purchase #5	$78.67	4.629%	$82.3116	$82.31	$82.30	$82.30
Purchase #6	$116.98	4.851%	$122.6547	$122.65	$122.65	$122.70
Purchase #7	$129.90	11.433%	$144.7515	$144.75	$144.75	$144.80
7 purchase totals =	$1,015.22		$1,105.6040	$1,105.60	$1,105.60	$1,105.60