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	$169.50	5.345%	$178.5598	$178.56	$178.55	$178.60
Purchase #2	$37.56	7.778%	$40.4814	$40.48	$40.50	$40.50
Purchase #3	$184.60	4.783%	$193.4294	$193.43	$193.45	$193.40
Purchase #4	$94.53	3.106%	$97.4661	$97.47	$97.45	$97.50
Purchase #5	$83.29	13.467%	$94.5067	$94.51	$94.50	$94.50
Purchase #6	$240.95	13.406%	$273.2518	$273.25	$273.25	$273.30
Purchase #7	$249.97	9.213%	$272.9997	$273.00	$273.00	$273.00
7 purchase totals =	$1,060.40		$1,150.6949	$1,150.70	$1,150.70	$1,150.80