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	$200.94	11.149%	$223.3428	$223.34	$223.35	$223.30
Purchase #2	$13.53	9.741%	$14.848	$14.85	$14.85	$14.80
Purchase #3	$51.59	8.587%	$56.02	$56.02	$56.00	$56.00
Purchase #4	$37.89	6.458%	$40.3369	$40.34	$40.35	$40.30
Purchase #5	$44.78	11.556%	$49.9548	$49.95	$49.95	$50.00
Purchase #6	$69.66	12.574%	$78.419	$78.42	$78.40	$78.40
Purchase #7	$132.88	9.273%	$145.202	$145.20	$145.20	$145.20
7 purchase totals =	$551.27		$608.1235	$608.12	$608.10	$608.00