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	$180.59	4.789%	$189.2385	$189.24	$189.25	$189.20
Purchase #2	$145.98	10.807%	$161.7561	$161.76	$161.75	$161.80
Purchase #3	$66.87	10.509%	$73.8974	$73.90	$73.90	$73.90
Purchase #4	$139.30	9.257%	$152.195	$152.20	$152.20	$152.20
Purchase #5	$118.42	7.279%	$127.0398	$127.04	$127.05	$127.00
Purchase #6	$186.68	7.582%	$200.8341	$200.83	$200.85	$200.80
Purchase #7	$112.59	6.110%	$119.4692	$119.47	$119.45	$119.50
7 purchase totals =	$950.43		$1,024.4301	$1,024.44	$1,024.45	$1,024.40