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	$126.71	5.706%	$133.9401	$133.94	$133.95	$133.90
Purchase #2	$70.34	11.305%	$78.2919	$78.29	$78.30	$78.30
Purchase #3	$151.89	5.247%	$159.8597	$159.86	$159.85	$159.90
Purchase #4	$73.89	6.549%	$78.7291	$78.73	$78.75	$78.70
Purchase #5	$118.50	13.870%	$134.936	$134.94	$134.95	$134.90
Purchase #6	$48.59	9.817%	$53.3601	$53.36	$53.35	$53.40
Purchase #7	$22.60	6.259%	$24.0145	$24.01	$24.00	$24.00
7 purchase totals =	$612.52		$663.1314	$663.13	$663.15	$663.10