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	$35.38	10.469%	$39.0839	$39.08	$39.10	$39.10
Purchase #2	$96.72	6.524%	$103.03	$103.03	$103.05	$103.00
Purchase #3	$225.75	13.597%	$256.4452	$256.45	$256.45	$256.40
Purchase #4	$154.94	6.854%	$165.5596	$165.56	$165.55	$165.60
Purchase #5	$16.37	11.213%	$18.2056	$18.21	$18.20	$18.20
Purchase #6	$214.76	13.405%	$243.5486	$243.55	$243.55	$243.50
Purchase #7	$182.90	3.139%	$188.6412	$188.64	$188.65	$188.60
7 purchase totals =	$926.82		$1,014.5141	$1,014.52	$1,014.55	$1,014.40