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	$82.72	4.207%	$86.2	$86.20	$86.20	$86.20
Purchase #2	$100.64	6.602%	$107.2843	$107.28	$107.30	$107.30
Purchase #3	$175.89	5.705%	$185.9245	$185.92	$185.90	$185.90
Purchase #4	$241.85	12.856%	$272.9422	$272.94	$272.95	$272.90
Purchase #5	$183.30	11.750%	$204.8378	$204.84	$204.85	$204.80
Purchase #6	$40.59	12.598%	$45.7035	$45.70	$45.70	$45.70
Purchase #7	$154.69	12.686%	$174.314	$174.31	$174.30	$174.30
7 purchase totals =	$979.68		$1,077.2063	$1,077.19	$1,077.20	$1,077.10