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	$216.26	6.372%	$230.0401	$230.04	$230.05	$230.00
Purchase #2	$116.40	5.681%	$123.0127	$123.01	$123.00	$123.00
Purchase #3	$175.52	6.594%	$187.0938	$187.09	$187.10	$187.10
Purchase #4	$51.73	11.122%	$57.4834	$57.48	$57.50	$57.50
Purchase #5	$186.32	5.256%	$196.113	$196.11	$196.10	$196.10
Purchase #6	$121.59	8.565%	$132.0042	$132.00	$132.00	$132.00
Purchase #7	$238.53	13.496%	$270.722	$270.72	$270.70	$270.70
7 purchase totals =	$1,106.35		$1,196.4692	$1,196.45	$1,196.45	$1,196.40