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	$192.91	12.729%	$217.4655	$217.47	$217.45	$217.50
Purchase #2	$212.85	12.211%	$238.8411	$238.84	$238.85	$238.80
Purchase #3	$117.32	5.388%	$123.6412	$123.64	$123.65	$123.60
Purchase #4	$185.62	12.339%	$208.5237	$208.52	$208.50	$208.50
Purchase #5	$48.59	11.552%	$54.2031	$54.20	$54.20	$54.20
Purchase #6	$77.63	10.398%	$85.702	$85.70	$85.70	$85.70
Purchase #7	$171.65	6.395%	$182.627	$182.63	$182.65	$182.60
7 purchase totals =	$1,006.57		$1,111.0036	$1,111.00	$1,111.00	$1,110.90