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	$204.76	7.374%	$219.859	$219.86	$219.85	$219.90
Purchase #2	$101.76	12.128%	$114.1015	$114.10	$114.10	$114.10
Purchase #3	$95.78	11.346%	$106.6472	$106.65	$106.65	$106.60
Purchase #4	$128.90	13.152%	$145.8529	$145.85	$145.85	$145.90
Purchase #5	$112.42	6.422%	$119.6396	$119.64	$119.65	$119.60
Purchase #6	$53.63	5.866%	$56.7759	$56.78	$56.80	$56.80
Purchase #7	$66.52	6.745%	$71.0068	$71.01	$71.00	$71.00
7 purchase totals =	$763.77		$833.8829	$833.89	$833.90	$833.90