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	$108.93	9.358%	$119.1237	$119.12	$119.10	$119.10
Purchase #2	$247.64	3.505%	$256.3198	$256.32	$256.30	$256.30
Purchase #3	$173.86	6.767%	$185.6251	$185.63	$185.65	$185.60
Purchase #4	$82.37	3.526%	$85.2744	$85.27	$85.25	$85.30
Purchase #5	$124.88	6.174%	$132.5901	$132.59	$132.60	$132.60
Purchase #6	$196.42	4.146%	$204.5636	$204.56	$204.55	$204.60
Purchase #7	$193.65	12.508%	$217.8717	$217.87	$217.85	$217.90
7 purchase totals =	$1,127.75		$1,201.3684	$1,201.36	$1,201.30	$1,201.40