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	$235.45	6.577%	$250.9355	$250.94	$250.95	$250.90
Purchase #2	$50.37	5.388%	$53.0839	$53.08	$53.10	$53.10
Purchase #3	$174.51	9.372%	$190.8651	$190.87	$190.85	$190.90
Purchase #4	$59.69	5.603%	$63.0344	$63.03	$63.05	$63.00
Purchase #5	$42.27	12.278%	$47.4599	$47.46	$47.45	$47.50
Purchase #6	$199.82	7.731%	$215.2681	$215.27	$215.25	$215.30
Purchase #7	$166.64	12.439%	$187.3683	$187.37	$187.35	$187.40
7 purchase totals =	$928.75		$1,008.0152	$1,008.02	$1,008.00	$1,008.10