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	$155.72	10.293%	$171.7483	$171.75	$171.75	$171.70
Purchase #2	$132.64	7.429%	$142.4938	$142.49	$142.50	$142.50
Purchase #3	$109.82	9.564%	$120.3232	$120.32	$120.30	$120.30
Purchase #4	$152.37	8.108%	$164.7242	$164.72	$164.70	$164.70
Purchase #5	$122.43	4.214%	$127.5892	$127.59	$127.60	$127.60
Purchase #6	$96.59	12.284%	$108.4551	$108.46	$108.45	$108.50
Purchase #7	$246.92	11.782%	$276.0121	$276.01	$276.00	$276.00
7 purchase totals =	$1,016.49		$1,111.3459	$1,111.34	$1,111.30	$1,111.30