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	$213.40	6.563%	$227.4054	$227.41	$227.40	$227.40
Purchase #2	$126.30	4.445%	$131.914	$131.91	$131.90	$131.90
Purchase #3	$26.80	9.406%	$29.3208	$29.32	$29.30	$29.30
Purchase #4	$160.47	7.120%	$171.8955	$171.90	$171.90	$171.90
Purchase #5	$126.76	8.596%	$137.6563	$137.66	$137.65	$137.70
Purchase #6	$111.44	10.491%	$123.1312	$123.13	$123.15	$123.10
Purchase #7	$77.76	6.145%	$82.5384	$82.54	$82.55	$82.50
7 purchase totals =	$842.93		$903.8616	$903.87	$903.85	$903.80