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	$123.26	7.865%	$132.9544	$132.95	$132.95	$133.00
Purchase #2	$168.96	6.458%	$179.8714	$179.87	$179.85	$179.90
Purchase #3	$163.92	8.542%	$177.922	$177.92	$177.90	$177.90
Purchase #4	$17.59	3.733%	$18.2466	$18.25	$18.25	$18.20
Purchase #5	$55.48	7.184%	$59.4657	$59.47	$59.45	$59.50
Purchase #6	$223.52	11.872%	$250.0563	$250.06	$250.05	$250.10
Purchase #7	$231.30	8.208%	$250.2851	$250.29	$250.30	$250.30
7 purchase totals =	$984.03		$1,068.8015	$1,068.81	$1,068.75	$1,068.90