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	$237.87	10.266%	$262.2897	$262.29	$262.30	$262.30
Purchase #2	$48.59	7.532%	$52.2498	$52.25	$52.25	$52.20
Purchase #3	$133.75	5.783%	$141.4848	$141.48	$141.50	$141.50
Purchase #4	$177.87	8.124%	$192.3202	$192.32	$192.30	$192.30
Purchase #5	$101.91	3.363%	$105.3372	$105.34	$105.35	$105.30
Purchase #6	$137.88	4.467%	$144.0391	$144.04	$144.05	$144.00
Purchase #7	$127.32	11.758%	$142.2903	$142.29	$142.30	$142.30
7 purchase totals =	$965.19		$1,040.0111	$1,040.01	$1,040.05	$1,039.90