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	$139.30	8.825%	$151.5932	$151.59	$151.60	$151.60
Purchase #2	$242.74	9.534%	$265.8828	$265.88	$265.90	$265.90
Purchase #3	$85.98	4.747%	$90.0615	$90.06	$90.05	$90.10
Purchase #4	$62.62	8.816%	$68.1406	$68.14	$68.15	$68.10
Purchase #5	$151.41	4.539%	$158.2825	$158.28	$158.30	$158.30
Purchase #6	$107.80	11.183%	$119.8553	$119.86	$119.85	$119.90
Purchase #7	$30.67	9.499%	$33.5833	$33.58	$33.60	$33.60
7 purchase totals =	$820.52		$887.3992	$887.39	$887.45	$887.50