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	$58.26	12.548%	$65.5705	$65.57	$65.55	$65.60
Purchase #2	$31.73	11.401%	$35.3475	$35.35	$35.35	$35.30
Purchase #3	$232.55	4.262%	$242.4613	$242.46	$242.45	$242.50
Purchase #4	$119.63	3.553%	$123.8805	$123.88	$123.90	$123.90
Purchase #5	$146.82	4.103%	$152.844	$152.84	$152.85	$152.80
Purchase #6	$23.80	3.352%	$24.5978	$24.60	$24.60	$24.60
Purchase #7	$240.98	5.479%	$254.1833	$254.18	$254.20	$254.20
7 purchase totals =	$853.77		$898.8849	$898.88	$898.90	$898.90