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	$106.27	4.524%	$111.0777	$111.08	$111.10	$111.10
Purchase #2	$221.38	7.667%	$238.3532	$238.35	$238.35	$238.40
Purchase #3	$116.95	7.382%	$125.5832	$125.58	$125.60	$125.60
Purchase #4	$14.89	7.788%	$16.0496	$16.05	$16.05	$16.00
Purchase #5	$108.32	13.442%	$122.8804	$122.88	$122.90	$122.90
Purchase #6	$123.91	13.470%	$140.6007	$140.60	$140.60	$140.60
Purchase #7	$163.63	13.635%	$185.941	$185.94	$185.95	$185.90
7 purchase totals =	$855.35		$940.4858	$940.48	$940.55	$940.50