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	$91.89	10.558%	$101.5917	$101.59	$101.60	$101.60
Purchase #2	$40.60	7.442%	$43.6215	$43.62	$43.60	$43.60
Purchase #3	$129.38	8.128%	$139.896	$139.90	$139.90	$139.90
Purchase #4	$104.74	7.630%	$112.7317	$112.73	$112.75	$112.70
Purchase #5	$32.38	5.202%	$34.0644	$34.06	$34.05	$34.10
Purchase #6	$197.25	6.111%	$209.3039	$209.30	$209.30	$209.30
Purchase #7	$150.78	4.380%	$157.3842	$157.38	$157.40	$157.40
7 purchase totals =	$747.02		$798.5934	$798.58	$798.60	$798.60