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	$104.51	13.519%	$118.6387	$118.64	$118.65	$118.60
Purchase #2	$28.43	12.425%	$31.9624	$31.96	$31.95	$32.00
Purchase #3	$29.46	9.401%	$32.2295	$32.23	$32.25	$32.20
Purchase #4	$40.36	7.387%	$43.3414	$43.34	$43.35	$43.30
Purchase #5	$72.25	11.383%	$80.4742	$80.47	$80.45	$80.50
Purchase #6	$100.59	3.137%	$103.7455	$103.75	$103.75	$103.70
Purchase #7	$58.78	4.367%	$61.3469	$61.35	$61.35	$61.30
7 purchase totals =	$434.38		$471.7386	$471.74	$471.75	$471.60