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	$206.95	4.675%	$216.6249	$216.62	$216.60	$216.60
Purchase #2	$87.40	8.363%	$94.7093	$94.71	$94.70	$94.70
Purchase #3	$137.92	4.109%	$143.5871	$143.59	$143.60	$143.60
Purchase #4	$169.67	9.418%	$185.6495	$185.65	$185.65	$185.60
Purchase #5	$20.51	5.485%	$21.635	$21.64	$21.65	$21.60
Purchase #6	$239.78	8.436%	$260.0078	$260.01	$260.00	$260.00
Purchase #7	$176.45	7.418%	$189.5391	$189.54	$189.55	$189.50
7 purchase totals =	$1,038.68		$1,111.7527	$1,111.76	$1,111.75	$1,111.60