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	$210.96	6.815%	$225.3369	$225.34	$225.35	$225.30
Purchase #2	$230.64	11.667%	$257.5488	$257.55	$257.55	$257.50
Purchase #3	$139.52	12.362%	$156.7675	$156.77	$156.75	$156.80
Purchase #4	$163.64	5.641%	$172.8709	$172.87	$172.85	$172.90
Purchase #5	$45.59	5.857%	$48.2602	$48.26	$48.25	$48.30
Purchase #6	$195.80	10.153%	$215.6796	$215.68	$215.70	$215.70
Purchase #7	$212.47	4.718%	$222.4943	$222.49	$222.50	$222.50
7 purchase totals =	$1,198.62		$1,298.9582	$1,298.96	$1,298.95	$1,299.00