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	$224.45	5.444%	$236.6691	$236.67	$236.65	$236.70
Purchase #2	$243.64	12.505%	$274.1072	$274.11	$274.10	$274.10
Purchase #3	$230.75	10.817%	$255.7102	$255.71	$255.70	$255.70
Purchase #4	$54.94	8.807%	$59.7786	$59.78	$59.80	$59.80
Purchase #5	$218.90	4.491%	$228.7308	$228.73	$228.75	$228.70
Purchase #6	$103.46	9.182%	$112.9597	$112.96	$112.95	$113.00
Purchase #7	$243.54	4.839%	$255.3249	$255.32	$255.30	$255.30
7 purchase totals =	$1,319.68		$1,423.2805	$1,423.28	$1,423.25	$1,423.30