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	$176.25	11.719%	$196.9047	$196.90	$196.90	$196.90
Purchase #2	$90.44	11.335%	$100.6914	$100.69	$100.70	$100.70
Purchase #3	$179.82	8.250%	$194.6552	$194.66	$194.65	$194.70
Purchase #4	$88.28	8.584%	$95.858	$95.86	$95.85	$95.90
Purchase #5	$150.73	11.193%	$167.6012	$167.60	$167.60	$167.60
Purchase #6	$36.29	7.104%	$38.868	$38.87	$38.85	$38.90
Purchase #7	$147.74	13.752%	$168.0572	$168.06	$168.05	$168.10
7 purchase totals =	$869.55		$962.6357	$962.64	$962.60	$962.80