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	$201.42	3.678%	$208.8282	$208.83	$208.85	$208.80
Purchase #2	$128.29	8.705%	$139.4576	$139.46	$139.45	$139.50
Purchase #3	$102.67	10.344%	$113.2902	$113.29	$113.30	$113.30
Purchase #4	$153.81	3.770%	$159.6086	$159.61	$159.60	$159.60
Purchase #5	$25.92	9.691%	$28.4319	$28.43	$28.45	$28.40
Purchase #6	$33.91	10.238%	$37.3817	$37.38	$37.40	$37.40
Purchase #7	$150.33	5.798%	$159.0461	$159.05	$159.05	$159.00
7 purchase totals =	$796.35		$846.0443	$846.05	$846.10	$846.00