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	$49.48	5.223%	$52.0643	$52.06	$52.05	$52.10
Purchase #2	$118.63	4.429%	$123.8841	$123.88	$123.90	$123.90
Purchase #3	$169.29	9.486%	$185.3488	$185.35	$185.35	$185.30
Purchase #4	$38.63	12.294%	$43.3792	$43.38	$43.40	$43.40
Purchase #5	$108.35	8.814%	$117.9	$117.90	$117.90	$117.90
Purchase #6	$123.29	7.255%	$132.2347	$132.23	$132.25	$132.20
Purchase #7	$121.72	10.702%	$134.7465	$134.75	$134.75	$134.70
7 purchase totals =	$729.39		$789.5576	$789.55	$789.60	$789.50