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	$237.87	5.746%	$251.538	$251.54	$251.55	$251.50
Purchase #2	$60.70	7.665%	$65.3527	$65.35	$65.35	$65.40
Purchase #3	$36.97	3.734%	$38.3505	$38.35	$38.35	$38.40
Purchase #4	$54.85	9.275%	$59.9373	$59.94	$59.95	$59.90
Purchase #5	$78.55	6.294%	$83.4939	$83.49	$83.50	$83.50
Purchase #6	$199.33	13.114%	$225.4701	$225.47	$225.45	$225.50
Purchase #7	$123.54	10.704%	$136.7637	$136.76	$136.75	$136.80
7 purchase totals =	$791.81		$860.9062	$860.90	$860.90	$861.00