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	$85.61	4.647%	$89.5883	$89.59	$89.60	$89.60
Purchase #2	$63.56	10.555%	$70.2688	$70.27	$70.25	$70.30
Purchase #3	$43.49	5.386%	$45.8324	$45.83	$45.85	$45.80
Purchase #4	$53.49	9.573%	$58.6106	$58.61	$58.60	$58.60
Purchase #5	$126.88	4.794%	$132.9626	$132.96	$132.95	$133.00
Purchase #6	$196.46	11.691%	$219.4281	$219.43	$219.45	$219.40
Purchase #7	$151.95	13.517%	$172.4891	$172.49	$172.50	$172.50
7 purchase totals =	$721.44		$789.1799	$789.18	$789.20	$789.20