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	$100.44	3.390%	$103.8449	$103.84	$103.85	$103.80
Purchase #2	$210.68	7.628%	$226.7507	$226.75	$226.75	$226.80
Purchase #3	$77.92	9.720%	$85.4938	$85.49	$85.50	$85.50
Purchase #4	$130.31	8.645%	$141.5753	$141.58	$141.60	$141.60
Purchase #5	$179.77	9.237%	$196.3754	$196.38	$196.40	$196.40
Purchase #6	$160.78	9.732%	$176.4271	$176.43	$176.45	$176.40
Purchase #7	$217.46	3.348%	$224.7406	$224.74	$224.75	$224.70
7 purchase totals =	$1,077.36		$1,155.2078	$1,155.21	$1,155.30	$1,155.20