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	$118.29	13.666%	$134.4555	$134.46	$134.45	$134.50
Purchase #2	$64.50	4.256%	$67.2451	$67.25	$67.25	$67.20
Purchase #3	$221.36	8.296%	$239.724	$239.72	$239.70	$239.70
Purchase #4	$211.53	12.789%	$238.5826	$238.58	$238.60	$238.60
Purchase #5	$96.46	3.502%	$99.838	$99.84	$99.85	$99.80
Purchase #6	$34.86	10.424%	$38.4938	$38.49	$38.50	$38.50
Purchase #7	$96.49	7.480%	$103.7075	$103.71	$103.70	$103.70
7 purchase totals =	$843.49		$922.0465	$922.05	$922.05	$922.00