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	$86.45	4.179%	$90.0627	$90.06	$90.05	$90.10
Purchase #2	$177.41	10.267%	$195.6247	$195.62	$195.60	$195.60
Purchase #3	$123.81	3.670%	$128.3538	$128.35	$128.35	$128.40
Purchase #4	$227.60	9.219%	$248.5824	$248.58	$248.60	$248.60
Purchase #5	$59.46	11.750%	$66.4466	$66.45	$66.45	$66.40
Purchase #6	$163.96	10.779%	$181.6332	$181.63	$181.65	$181.60
Purchase #7	$115.37	7.434%	$123.9466	$123.95	$123.95	$123.90
7 purchase totals =	$954.06		$1,034.6500	$1,034.64	$1,034.65	$1,034.60