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	$228.37	5.568%	$241.0856	$241.09	$241.10	$241.10
Purchase #2	$189.81	10.697%	$210.114	$210.11	$210.10	$210.10
Purchase #3	$82.75	3.141%	$85.3492	$85.35	$85.35	$85.30
Purchase #4	$150.71	5.522%	$159.0322	$159.03	$159.05	$159.00
Purchase #5	$119.31	11.868%	$133.4697	$133.47	$133.45	$133.50
Purchase #6	$50.94	7.142%	$54.5781	$54.58	$54.60	$54.60
Purchase #7	$56.46	5.818%	$59.7448	$59.74	$59.75	$59.70
7 purchase totals =	$878.35		$943.3736	$943.37	$943.40	$943.30