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	$237.85	5.851%	$251.7666	$251.77	$251.75	$251.80
Purchase #2	$54.44	8.550%	$59.0946	$59.09	$59.10	$59.10
Purchase #3	$164.40	9.115%	$179.3851	$179.39	$179.40	$179.40
Purchase #4	$179.95	8.627%	$195.4743	$195.47	$195.45	$195.50
Purchase #5	$231.62	9.566%	$253.7768	$253.78	$253.80	$253.80
Purchase #6	$76.68	4.500%	$80.1306	$80.13	$80.15	$80.10
Purchase #7	$176.51	11.287%	$196.4327	$196.43	$196.45	$196.40
7 purchase totals =	$1,121.45		$1,216.0607	$1,216.06	$1,216.10	$1,216.10