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	$163.43	4.638%	$171.0099	$171.01	$171.00	$171.00
Purchase #2	$200.37	6.255%	$212.9031	$212.90	$212.90	$212.90
Purchase #3	$107.46	5.693%	$113.5777	$113.58	$113.60	$113.60
Purchase #4	$40.36	5.781%	$42.6932	$42.69	$42.70	$42.70
Purchase #5	$213.43	8.679%	$231.9536	$231.95	$231.95	$232.00
Purchase #6	$119.69	11.152%	$133.0378	$133.04	$133.05	$133.00
Purchase #7	$69.42	5.705%	$73.3804	$73.38	$73.40	$73.40
7 purchase totals =	$914.16		$978.5557	$978.55	$978.60	$978.60