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	$232.63	10.342%	$256.6886	$256.69	$256.70	$256.70
Purchase #2	$39.32	8.321%	$42.5918	$42.59	$42.60	$42.60
Purchase #3	$153.93	8.196%	$166.5461	$166.55	$166.55	$166.50
Purchase #4	$167.93	11.816%	$187.7726	$187.77	$187.75	$187.80
Purchase #5	$168.71	11.238%	$187.6696	$187.67	$187.65	$187.70
Purchase #6	$241.97	10.116%	$266.4477	$266.45	$266.45	$266.40
Purchase #7	$66.65	11.807%	$74.5194	$74.52	$74.50	$74.50
7 purchase totals =	$1,071.14		$1,182.2358	$1,182.24	$1,182.20	$1,182.20