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	$105.90	5.396%	$111.6144	$111.61	$111.60	$111.60
Purchase #2	$169.61	10.107%	$186.7525	$186.75	$186.75	$186.80
Purchase #3	$89.93	4.792%	$94.2394	$94.24	$94.25	$94.20
Purchase #4	$151.36	3.493%	$156.647	$156.65	$156.65	$156.60
Purchase #5	$242.29	10.178%	$266.9503	$266.95	$266.95	$267.00
Purchase #6	$162.43	3.806%	$168.6121	$168.61	$168.60	$168.60
Purchase #7	$148.29	7.198%	$158.9639	$158.96	$158.95	$159.00
7 purchase totals =	$1,069.81		$1,143.7796	$1,143.77	$1,143.75	$1,143.80