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	$80.87	11.612%	$90.2606	$90.26	$90.25	$90.30
Purchase #2	$97.72	3.309%	$100.9536	$100.95	$100.95	$101.00
Purchase #3	$213.27	3.720%	$221.2036	$221.20	$221.20	$221.20
Purchase #4	$180.99	10.770%	$200.4826	$200.48	$200.50	$200.50
Purchase #5	$124.40	6.168%	$132.073	$132.07	$132.05	$132.10
Purchase #6	$180.26	10.143%	$198.5438	$198.54	$198.55	$198.50
Purchase #7	$152.38	9.664%	$167.106	$167.11	$167.10	$167.10
7 purchase totals =	$1,029.89		$1,110.6232	$1,110.61	$1,110.60	$1,110.70