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	$23.86	8.805%	$25.9609	$25.96	$25.95	$26.00
Purchase #2	$50.76	12.521%	$57.1157	$57.12	$57.10	$57.10
Purchase #3	$129.66	12.293%	$145.5991	$145.60	$145.60	$145.60
Purchase #4	$80.30	10.845%	$89.0085	$89.01	$89.00	$89.00
Purchase #5	$46.92	3.399%	$48.5148	$48.51	$48.50	$48.50
Purchase #6	$89.86	13.357%	$101.8626	$101.86	$101.85	$101.90
Purchase #7	$95.47	10.458%	$105.4543	$105.45	$105.45	$105.50
7 purchase totals =	$516.83		$573.5159	$573.51	$573.45	$573.60