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	$141.37	10.378%	$156.0414	$156.04	$156.05	$156.00
Purchase #2	$40.42	10.323%	$44.5926	$44.59	$44.60	$44.60
Purchase #3	$61.77	4.705%	$64.6763	$64.68	$64.70	$64.70
Purchase #4	$62.81	7.567%	$67.5628	$67.56	$67.55	$67.60
Purchase #5	$81.50	9.769%	$89.4617	$89.46	$89.45	$89.50
Purchase #6	$217.65	12.401%	$244.6408	$244.64	$244.65	$244.60
Purchase #7	$102.72	8.319%	$111.2653	$111.27	$111.25	$111.30
7 purchase totals =	$708.24		$778.2409	$778.24	$778.25	$778.30