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	$15.83	4.117%	$16.4817	$16.48	$16.50	$16.50
Purchase #2	$77.61	13.857%	$88.3644	$88.36	$88.35	$88.40
Purchase #3	$240.91	10.594%	$266.432	$266.43	$266.45	$266.40
Purchase #4	$226.82	5.213%	$238.6441	$238.64	$238.65	$238.60
Purchase #5	$172.89	7.472%	$185.8083	$185.81	$185.80	$185.80
Purchase #6	$33.88	10.493%	$37.435	$37.44	$37.45	$37.40
Purchase #7	$219.67	6.785%	$234.5746	$234.57	$234.55	$234.60
7 purchase totals =	$987.61		$1,067.7401	$1,067.73	$1,067.75	$1,067.70