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	$130.35	4.752%	$136.5442	$136.54	$136.55	$136.50
Purchase #2	$234.54	9.331%	$256.4249	$256.42	$256.40	$256.40
Purchase #3	$171.89	6.178%	$182.5094	$182.51	$182.50	$182.50
Purchase #4	$80.81	11.847%	$90.3836	$90.38	$90.40	$90.40
Purchase #5	$239.69	7.221%	$256.998	$257.00	$257.00	$257.00
Purchase #6	$230.51	12.240%	$258.7244	$258.72	$258.70	$258.70
Purchase #7	$79.92	7.693%	$86.0682	$86.07	$86.05	$86.10
7 purchase totals =	$1,167.71		$1,267.6527	$1,267.64	$1,267.60	$1,267.60