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	$244.61	3.576%	$253.3573	$253.36	$253.35	$253.40
Purchase #2	$131.68	9.328%	$143.9631	$143.96	$143.95	$144.00
Purchase #3	$40.82	4.617%	$42.7047	$42.70	$42.70	$42.70
Purchase #4	$37.66	4.393%	$39.3144	$39.31	$39.30	$39.30
Purchase #5	$237.81	8.851%	$258.8586	$258.86	$258.85	$258.90
Purchase #6	$183.30	3.810%	$190.2837	$190.28	$190.30	$190.30
Purchase #7	$80.43	3.481%	$83.2298	$83.23	$83.25	$83.20
7 purchase totals =	$956.31		$1,011.7116	$1,011.70	$1,011.70	$1,011.80