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	$185.96	12.202%	$208.6508	$208.65	$208.65	$208.70
Purchase #2	$230.46	12.417%	$259.0762	$259.08	$259.10	$259.10
Purchase #3	$109.71	12.412%	$123.3272	$123.33	$123.35	$123.30
Purchase #4	$142.60	5.531%	$150.4872	$150.49	$150.50	$150.50
Purchase #5	$77.85	9.550%	$85.2847	$85.28	$85.30	$85.30
Purchase #6	$127.93	12.102%	$143.4121	$143.41	$143.40	$143.40
Purchase #7	$99.83	10.341%	$110.1534	$110.15	$110.15	$110.20
7 purchase totals =	$974.34		$1,080.3916	$1,080.39	$1,080.45	$1,080.50