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	$40.68	9.771%	$44.6548	$44.65	$44.65	$44.70
Purchase #2	$145.67	6.731%	$155.475	$155.48	$155.50	$155.50
Purchase #3	$123.91	6.233%	$131.6333	$131.63	$131.65	$131.60
Purchase #4	$72.42	8.628%	$78.6684	$78.67	$78.65	$78.70
Purchase #5	$55.77	10.496%	$61.6236	$61.62	$61.60	$61.60
Purchase #6	$99.32	3.133%	$102.4317	$102.43	$102.45	$102.40
Purchase #7	$83.25	11.123%	$92.5099	$92.51	$92.50	$92.50
7 purchase totals =	$621.02		$666.9967	$666.99	$667.00	$667.00