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	$72.39	8.580%	$78.6011	$78.60	$78.60	$78.60
Purchase #2	$194.66	8.454%	$211.1166	$211.12	$211.10	$211.10
Purchase #3	$13.84	10.541%	$15.2989	$15.30	$15.30	$15.30
Purchase #4	$113.82	13.179%	$128.8203	$128.82	$128.80	$128.80
Purchase #5	$241.98	6.381%	$257.4207	$257.42	$257.40	$257.40
Purchase #6	$68.81	4.199%	$71.6993	$71.70	$71.70	$71.70
Purchase #7	$112.51	12.487%	$126.5591	$126.56	$126.55	$126.60
7 purchase totals =	$818.01		$889.5160	$889.52	$889.45	$889.50