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	$226.99	4.766%	$237.8083	$237.81	$237.80	$237.80
Purchase #2	$152.46	12.494%	$171.5084	$171.51	$171.50	$171.50
Purchase #3	$38.44	11.639%	$42.914	$42.91	$42.90	$42.90
Purchase #4	$219.49	5.341%	$231.213	$231.21	$231.20	$231.20
Purchase #5	$228.80	12.169%	$256.6427	$256.64	$256.65	$256.60
Purchase #6	$115.27	9.617%	$126.3555	$126.36	$126.35	$126.40
Purchase #7	$19.86	3.681%	$20.591	$20.59	$20.60	$20.60
7 purchase totals =	$1,001.31		$1,087.0329	$1,087.03	$1,087.00	$1,087.00