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	$97.34	12.583%	$109.5883	$109.59	$109.60	$109.60
Purchase #2	$12.70	7.314%	$13.6289	$13.63	$13.65	$13.60
Purchase #3	$86.64	5.741%	$91.614	$91.61	$91.60	$91.60
Purchase #4	$178.27	5.766%	$188.549	$188.55	$188.55	$188.50
Purchase #5	$144.67	12.566%	$162.8492	$162.85	$162.85	$162.80
Purchase #6	$182.62	5.473%	$192.6148	$192.61	$192.60	$192.60
Purchase #7	$241.60	8.577%	$262.322	$262.32	$262.30	$262.30
7 purchase totals =	$943.84		$1,021.1662	$1,021.16	$1,021.15	$1,021.00