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	$128.95	6.792%	$137.7083	$137.71	$137.70	$137.70
Purchase #2	$216.71	3.250%	$223.7531	$223.75	$223.75	$223.80
Purchase #3	$90.82	13.596%	$103.1679	$103.17	$103.15	$103.20
Purchase #4	$210.69	6.248%	$223.8539	$223.85	$223.85	$223.90
Purchase #5	$15.99	9.231%	$17.466	$17.47	$17.45	$17.50
Purchase #6	$165.95	3.834%	$172.3125	$172.31	$172.30	$172.30
Purchase #7	$214.67	3.831%	$222.894	$222.89	$222.90	$222.90
7 purchase totals =	$1,043.78		$1,101.1557	$1,101.15	$1,101.10	$1,101.30