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	$84.43	12.824%	$95.2573	$95.26	$95.25	$95.30
Purchase #2	$40.78	3.262%	$42.1102	$42.11	$42.10	$42.10
Purchase #3	$116.88	3.256%	$120.6856	$120.69	$120.70	$120.70
Purchase #4	$132.96	10.147%	$146.4515	$146.45	$146.45	$146.50
Purchase #5	$107.51	3.278%	$111.0342	$111.03	$111.05	$111.00
Purchase #6	$38.81	6.511%	$41.3369	$41.34	$41.35	$41.30
Purchase #7	$87.65	13.192%	$99.2128	$99.21	$99.20	$99.20
7 purchase totals =	$609.02		$656.0885	$656.09	$656.10	$656.10