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	$121.85	3.434%	$126.0343	$126.03	$126.05	$126.00
Purchase #2	$40.62	5.264%	$42.7582	$42.76	$42.75	$42.80
Purchase #3	$25.91	9.729%	$28.4308	$28.43	$28.45	$28.40
Purchase #4	$108.67	6.834%	$116.0965	$116.10	$116.10	$116.10
Purchase #5	$200.51	13.166%	$226.9091	$226.91	$226.90	$226.90
Purchase #6	$214.55	4.223%	$223.6104	$223.61	$223.60	$223.60
Purchase #7	$206.59	3.711%	$214.2566	$214.26	$214.25	$214.30
7 purchase totals =	$918.70		$978.0959	$978.10	$978.10	$978.10