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	$142.62	9.116%	$155.6212	$155.62	$155.60	$155.60
Purchase #2	$104.85	4.828%	$109.9122	$109.91	$109.90	$109.90
Purchase #3	$142.39	10.542%	$157.4008	$157.40	$157.40	$157.40
Purchase #4	$38.77	7.774%	$41.784	$41.78	$41.80	$41.80
Purchase #5	$199.97	11.466%	$222.8986	$222.90	$222.90	$222.90
Purchase #6	$143.53	3.473%	$148.5148	$148.51	$148.50	$148.50
Purchase #7	$102.51	5.479%	$108.1265	$108.13	$108.15	$108.10
7 purchase totals =	$874.64		$944.2581	$944.25	$944.25	$944.20