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	$99.54	4.360%	$103.8799	$103.88	$103.90	$103.90
Purchase #2	$158.77	8.576%	$172.3861	$172.39	$172.40	$172.40
Purchase #3	$178.39	3.361%	$184.3857	$184.39	$184.40	$184.40
Purchase #4	$228.80	4.118%	$238.222	$238.22	$238.20	$238.20
Purchase #5	$49.51	6.409%	$52.6831	$52.68	$52.70	$52.70
Purchase #6	$237.78	7.498%	$255.6087	$255.61	$255.60	$255.60
Purchase #7	$33.75	12.218%	$37.8736	$37.87	$37.85	$37.90
7 purchase totals =	$986.54		$1,045.0391	$1,045.04	$1,045.05	$1,045.10