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	$99.49	5.619%	$105.0803	$105.08	$105.10	$105.10
Purchase #2	$200.59	10.806%	$222.2658	$222.27	$222.25	$222.30
Purchase #3	$54.42	3.381%	$56.2599	$56.26	$56.25	$56.30
Purchase #4	$182.89	4.255%	$190.672	$190.67	$190.65	$190.70
Purchase #5	$191.68	8.718%	$208.3907	$208.39	$208.40	$208.40
Purchase #6	$166.54	6.385%	$177.1736	$177.17	$177.15	$177.20
Purchase #7	$139.51	9.334%	$152.5319	$152.53	$152.55	$152.50
7 purchase totals =	$1,035.12		$1,112.3742	$1,112.37	$1,112.35	$1,112.50