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	$222.61	9.756%	$244.3278	$244.33	$244.35	$244.30
Purchase #2	$104.58	11.304%	$116.4017	$116.40	$116.40	$116.40
Purchase #3	$132.34	10.421%	$146.1312	$146.13	$146.15	$146.10
Purchase #4	$55.35	11.749%	$61.8531	$61.85	$61.85	$61.90
Purchase #5	$160.28	11.297%	$178.3868	$178.39	$178.40	$178.40
Purchase #6	$58.40	13.550%	$66.3132	$66.31	$66.30	$66.30
Purchase #7	$139.31	3.685%	$144.4436	$144.44	$144.45	$144.40
7 purchase totals =	$872.87		$957.8574	$957.85	$957.90	$957.80