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	$227.57	6.284%	$241.8705	$241.87	$241.85	$241.90
Purchase #2	$219.65	13.733%	$249.8145	$249.81	$249.80	$249.80
Purchase #3	$52.83	12.743%	$59.5621	$59.56	$59.55	$59.60
Purchase #4	$65.59	9.155%	$71.5948	$71.59	$71.60	$71.60
Purchase #5	$210.84	4.487%	$220.3004	$220.30	$220.30	$220.30
Purchase #6	$126.82	6.175%	$134.6511	$134.65	$134.65	$134.70
Purchase #7	$135.41	10.453%	$149.5644	$149.56	$149.55	$149.60
7 purchase totals =	$1,038.71		$1,127.3578	$1,127.34	$1,127.30	$1,127.50