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	$117.85	13.334%	$133.5641	$133.56	$133.55	$133.60
Purchase #2	$106.97	11.672%	$119.4555	$119.46	$119.45	$119.50
Purchase #3	$240.33	7.309%	$257.8957	$257.90	$257.90	$257.90
Purchase #4	$154.87	13.241%	$175.3763	$175.38	$175.40	$175.40
Purchase #5	$127.62	13.242%	$144.5194	$144.52	$144.50	$144.50
Purchase #6	$52.78	5.351%	$55.6043	$55.60	$55.60	$55.60
Purchase #7	$161.63	4.255%	$168.5074	$168.51	$168.50	$168.50
7 purchase totals =	$962.05		$1,054.9227	$1,054.93	$1,054.90	$1,055.00