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	$184.87	4.715%	$193.5866	$193.59	$193.60	$193.60
Purchase #2	$18.50	8.451%	$20.0634	$20.06	$20.05	$20.10
Purchase #3	$10.63	3.670%	$11.0201	$11.02	$11.00	$11.00
Purchase #4	$145.56	3.631%	$150.8453	$150.85	$150.85	$150.80
Purchase #5	$40.77	6.640%	$43.4771	$43.48	$43.50	$43.50
Purchase #6	$78.56	5.564%	$82.9311	$82.93	$82.95	$82.90
Purchase #7	$159.93	10.684%	$177.0169	$177.02	$177.00	$177.00
7 purchase totals =	$638.82		$678.9405	$678.95	$678.95	$678.90