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	$111.96	9.722%	$122.8448	$122.84	$122.85	$122.80
Purchase #2	$12.29	9.546%	$13.4632	$13.46	$13.45	$13.50
Purchase #3	$61.51	13.769%	$69.9793	$69.98	$70.00	$70.00
Purchase #4	$231.31	13.396%	$262.2963	$262.30	$262.30	$262.30
Purchase #5	$86.76	3.655%	$89.9311	$89.93	$89.95	$89.90
Purchase #6	$116.59	13.712%	$132.5768	$132.58	$132.60	$132.60
Purchase #7	$128.85	13.524%	$146.2757	$146.28	$146.30	$146.30
7 purchase totals =	$749.27		$837.3672	$837.37	$837.45	$837.40