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	$43.44	9.407%	$47.5264	$47.53	$47.55	$47.50
Purchase #2	$112.45	9.469%	$123.0979	$123.10	$123.10	$123.10
Purchase #3	$99.75	3.648%	$103.3889	$103.39	$103.40	$103.40
Purchase #4	$145.28	11.318%	$161.7228	$161.72	$161.70	$161.70
Purchase #5	$90.25	11.677%	$100.7885	$100.79	$100.80	$100.80
Purchase #6	$113.68	5.168%	$119.555	$119.56	$119.55	$119.60
Purchase #7	$35.45	8.175%	$38.348	$38.35	$38.35	$38.30
7 purchase totals =	$640.30		$694.4275	$694.44	$694.45	$694.40