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	$171.29	5.458%	$180.639	$180.64	$180.65	$180.60
Purchase #2	$40.65	9.763%	$44.6187	$44.62	$44.60	$44.60
Purchase #3	$231.93	10.495%	$256.2711	$256.27	$256.25	$256.30
Purchase #4	$73.83	5.702%	$78.0398	$78.04	$78.05	$78.00
Purchase #5	$101.87	13.758%	$115.8853	$115.89	$115.90	$115.90
Purchase #6	$165.36	6.146%	$175.523	$175.52	$175.50	$175.50
Purchase #7	$144.62	10.708%	$160.1059	$160.11	$160.10	$160.10
7 purchase totals =	$929.55		$1,011.0828	$1,011.09	$1,011.05	$1,011.00