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	$247.50	7.649%	$266.4313	$266.43	$266.45	$266.40
Purchase #2	$117.49	8.151%	$127.0666	$127.07	$127.05	$127.10
Purchase #3	$116.34	11.422%	$129.6284	$129.63	$129.65	$129.60
Purchase #4	$161.69	6.680%	$172.4909	$172.49	$172.50	$172.50
Purchase #5	$9.40	10.374%	$10.3752	$10.38	$10.40	$10.40
Purchase #6	$240.78	13.754%	$273.8969	$273.90	$273.90	$273.90
Purchase #7	$162.45	6.366%	$172.7916	$172.79	$172.80	$172.80
7 purchase totals =	$1,055.65		$1,152.6809	$1,152.69	$1,152.75	$1,152.70