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	$120.83	3.825%	$125.4517	$125.45	$125.45	$125.50
Purchase #2	$123.56	13.623%	$140.3926	$140.39	$140.40	$140.40
Purchase #3	$179.41	9.774%	$196.9455	$196.95	$196.95	$196.90
Purchase #4	$155.36	5.809%	$164.3849	$164.38	$164.40	$164.40
Purchase #5	$112.68	12.751%	$127.0478	$127.05	$127.05	$127.00
Purchase #6	$231.60	10.522%	$255.969	$255.97	$255.95	$256.00
Purchase #7	$140.53	8.484%	$152.4526	$152.45	$152.45	$152.50
7 purchase totals =	$1,063.97		$1,162.6441	$1,162.64	$1,162.65	$1,162.70