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	$78.42	5.546%	$82.7692	$82.77	$82.75	$82.80
Purchase #2	$146.26	6.853%	$156.2832	$156.28	$156.30	$156.30
Purchase #3	$62.72	6.362%	$66.7102	$66.71	$66.70	$66.70
Purchase #4	$244.51	13.125%	$276.6019	$276.60	$276.60	$276.60
Purchase #5	$194.35	10.799%	$215.3379	$215.34	$215.35	$215.30
Purchase #6	$98.94	13.227%	$112.0268	$112.03	$112.05	$112.00
Purchase #7	$93.82	5.373%	$98.8609	$98.86	$98.85	$98.90
7 purchase totals =	$919.02		$1,008.5901	$1,008.59	$1,008.60	$1,008.60