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	$158.98	11.688%	$177.5616	$177.56	$177.55	$177.60
Purchase #2	$88.43	4.568%	$92.4695	$92.47	$92.45	$92.50
Purchase #3	$223.34	8.452%	$242.2167	$242.22	$242.20	$242.20
Purchase #4	$230.59	10.816%	$255.5306	$255.53	$255.55	$255.50
Purchase #5	$212.47	5.448%	$224.0454	$224.05	$224.05	$224.00
Purchase #6	$116.43	12.127%	$130.5495	$130.55	$130.55	$130.50
Purchase #7	$151.53	9.272%	$165.5799	$165.58	$165.60	$165.60
7 purchase totals =	$1,181.77		$1,287.9532	$1,287.96	$1,287.95	$1,287.90