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	$136.42	3.774%	$141.5685	$141.57	$141.55	$141.60
Purchase #2	$237.28	3.544%	$245.6892	$245.69	$245.70	$245.70
Purchase #3	$10.52	10.283%	$11.6018	$11.60	$11.60	$11.60
Purchase #4	$250.75	11.522%	$279.6414	$279.64	$279.65	$279.60
Purchase #5	$194.60	10.211%	$214.4706	$214.47	$214.45	$214.50
Purchase #6	$148.82	4.366%	$155.3175	$155.32	$155.30	$155.30
Purchase #7	$35.63	5.263%	$37.5052	$37.51	$37.50	$37.50
7 purchase totals =	$1,014.02		$1,085.7942	$1,085.80	$1,085.75	$1,085.80