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	$90.99	5.558%	$96.0472	$96.05	$96.05	$96.00
Purchase #2	$96.54	7.181%	$103.4725	$103.47	$103.45	$103.50
Purchase #3	$196.68	13.343%	$222.923	$222.92	$222.90	$222.90
Purchase #4	$81.78	13.550%	$92.8612	$92.86	$92.85	$92.90
Purchase #5	$147.64	10.410%	$163.0093	$163.01	$163.00	$163.00
Purchase #6	$81.94	12.831%	$92.4537	$92.45	$92.45	$92.50
Purchase #7	$52.77	9.262%	$57.6576	$57.66	$57.65	$57.70
7 purchase totals =	$748.34		$828.4245	$828.42	$828.35	$828.50