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	$212.34	6.334%	$225.7896	$225.79	$225.80	$225.80
Purchase #2	$29.95	10.859%	$33.2023	$33.20	$33.20	$33.20
Purchase #3	$58.85	4.737%	$61.6377	$61.64	$61.65	$61.60
Purchase #4	$54.89	11.603%	$61.2589	$61.26	$61.25	$61.30
Purchase #5	$108.46	7.477%	$116.5696	$116.57	$116.55	$116.60
Purchase #6	$238.46	9.667%	$261.5119	$261.51	$261.50	$261.50
Purchase #7	$95.90	9.603%	$105.1093	$105.11	$105.10	$105.10
7 purchase totals =	$798.85		$865.0793	$865.08	$865.05	$865.10