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	$172.97	11.304%	$192.5225	$192.52	$192.50	$192.50
Purchase #2	$27.32	8.766%	$29.7149	$29.71	$29.70	$29.70
Purchase #3	$153.53	8.696%	$166.881	$166.88	$166.90	$166.90
Purchase #4	$78.60	4.515%	$82.1488	$82.15	$82.15	$82.10
Purchase #5	$177.48	4.738%	$185.889	$185.89	$185.90	$185.90
Purchase #6	$238.88	13.468%	$271.0524	$271.05	$271.05	$271.10
Purchase #7	$135.59	11.307%	$150.9212	$150.92	$150.90	$150.90
7 purchase totals =	$984.37		$1,079.1298	$1,079.12	$1,079.10	$1,079.10