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	$141.61	6.865%	$151.3315	$151.33	$151.35	$151.30
Purchase #2	$95.32	10.608%	$105.4315	$105.43	$105.45	$105.40
Purchase #3	$19.43	9.641%	$21.3032	$21.30	$21.30	$21.30
Purchase #4	$75.81	3.579%	$78.5232	$78.52	$78.50	$78.50
Purchase #5	$63.59	10.313%	$70.148	$70.15	$70.15	$70.10
Purchase #6	$236.58	13.761%	$269.1358	$269.14	$269.15	$269.10
Purchase #7	$126.34	10.571%	$139.6954	$139.70	$139.70	$139.70
7 purchase totals =	$758.68		$835.5686	$835.57	$835.60	$835.40