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	$48.97	11.573%	$54.6373	$54.64	$54.65	$54.60
Purchase #2	$131.75	12.818%	$148.6377	$148.64	$148.65	$148.60
Purchase #3	$235.32	9.407%	$257.4566	$257.46	$257.45	$257.50
Purchase #4	$80.45	12.446%	$90.4628	$90.46	$90.45	$90.50
Purchase #5	$221.51	10.521%	$244.8151	$244.82	$244.80	$244.80
Purchase #6	$20.94	13.597%	$23.7872	$23.79	$23.80	$23.80
Purchase #7	$168.33	10.588%	$186.1528	$186.15	$186.15	$186.20
7 purchase totals =	$907.27		$1,005.9495	$1,005.96	$1,005.95	$1,006.00