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	$218.59	13.792%	$248.7379	$248.74	$248.75	$248.70
Purchase #2	$19.46	11.416%	$21.6816	$21.68	$21.70	$21.70
Purchase #3	$142.32	6.188%	$151.1268	$151.13	$151.15	$151.10
Purchase #4	$68.39	13.339%	$77.5125	$77.51	$77.50	$77.50
Purchase #5	$90.26	11.164%	$100.3366	$100.34	$100.35	$100.30
Purchase #6	$224.81	4.334%	$234.5533	$234.55	$234.55	$234.60
Purchase #7	$169.90	5.421%	$179.1103	$179.11	$179.10	$179.10
7 purchase totals =	$933.73		$1,013.0590	$1,013.06	$1,013.10	$1,013.00