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	$213.72	3.477%	$221.151	$221.15	$221.15	$221.20
Purchase #2	$249.56	13.148%	$282.3721	$282.37	$282.35	$282.40
Purchase #3	$34.60	13.556%	$39.2904	$39.29	$39.30	$39.30
Purchase #4	$53.88	4.576%	$56.3455	$56.35	$56.35	$56.30
Purchase #5	$123.80	12.532%	$139.3146	$139.31	$139.30	$139.30
Purchase #6	$172.52	13.792%	$196.314	$196.31	$196.30	$196.30
Purchase #7	$127.29	11.163%	$141.4994	$141.50	$141.50	$141.50
7 purchase totals =	$975.37		$1,076.2870	$1,076.28	$1,076.25	$1,076.30