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	$112.85	9.848%	$123.9635	$123.96	$123.95	$124.00
Purchase #2	$189.89	7.446%	$204.0292	$204.03	$204.05	$204.00
Purchase #3	$103.75	3.810%	$107.7029	$107.70	$107.70	$107.70
Purchase #4	$88.98	12.461%	$100.0678	$100.07	$100.05	$100.10
Purchase #5	$132.69	4.621%	$138.8216	$138.82	$138.80	$138.80
Purchase #6	$237.74	11.511%	$265.1063	$265.11	$265.10	$265.10
Purchase #7	$247.51	3.798%	$256.9104	$256.91	$256.90	$256.90
7 purchase totals =	$1,113.41		$1,196.6017	$1,196.60	$1,196.55	$1,196.60