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	$107.83	5.411%	$113.6647	$113.66	$113.65	$113.70
Purchase #2	$38.42	9.578%	$42.0999	$42.10	$42.10	$42.10
Purchase #3	$75.84	9.855%	$83.314	$83.31	$83.30	$83.30
Purchase #4	$93.92	5.649%	$99.2255	$99.23	$99.25	$99.20
Purchase #5	$107.58	8.474%	$116.6963	$116.70	$116.70	$116.70
Purchase #6	$52.25	7.307%	$56.0679	$56.07	$56.05	$56.10
Purchase #7	$154.73	11.541%	$172.5874	$172.59	$172.60	$172.60
7 purchase totals =	$630.57		$683.6557	$683.66	$683.65	$683.70