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	$208.73	11.790%	$233.3393	$233.34	$233.35	$233.30
Purchase #2	$208.65	5.186%	$219.4706	$219.47	$219.45	$219.50
Purchase #3	$177.71	8.276%	$192.4173	$192.42	$192.40	$192.40
Purchase #4	$5.69	10.663%	$6.2967	$6.30	$6.30	$6.30
Purchase #5	$46.59	13.390%	$52.8284	$52.83	$52.85	$52.80
Purchase #6	$99.39	6.513%	$105.8633	$105.86	$105.85	$105.90
Purchase #7	$85.81	3.570%	$88.8734	$88.87	$88.85	$88.90
7 purchase totals =	$832.57		$899.0890	$899.09	$899.05	$899.10