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	$132.68	5.414%	$139.8633	$139.86	$139.85	$139.90
Purchase #2	$174.86	3.835%	$181.5659	$181.57	$181.55	$181.60
Purchase #3	$98.29	7.140%	$105.3079	$105.31	$105.30	$105.30
Purchase #4	$211.97	4.154%	$220.7752	$220.78	$220.80	$220.80
Purchase #5	$166.50	6.628%	$177.5356	$177.54	$177.55	$177.50
Purchase #6	$182.67	9.621%	$200.2447	$200.24	$200.25	$200.20
Purchase #7	$177.81	7.573%	$191.2756	$191.28	$191.30	$191.30
7 purchase totals =	$1,144.78		$1,216.5682	$1,216.58	$1,216.60	$1,216.60