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	$47.72	9.778%	$52.3861	$52.39	$52.40	$52.40
Purchase #2	$134.42	6.341%	$142.9436	$142.94	$142.95	$142.90
Purchase #3	$136.89	6.285%	$145.4935	$145.49	$145.50	$145.50
Purchase #4	$132.56	11.813%	$148.2193	$148.22	$148.20	$148.20
Purchase #5	$153.34	10.673%	$169.706	$169.71	$169.70	$169.70
Purchase #6	$214.26	9.179%	$233.9269	$233.93	$233.95	$233.90
Purchase #7	$52.29	12.588%	$58.8723	$58.87	$58.85	$58.90
7 purchase totals =	$871.48		$951.5477	$951.55	$951.55	$951.50