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	$121.60	10.689%	$134.5978	$134.60	$134.60	$134.60
Purchase #2	$154.65	11.108%	$171.8285	$171.83	$171.85	$171.80
Purchase #3	$236.94	10.725%	$262.3518	$262.35	$262.35	$262.40
Purchase #4	$89.43	13.556%	$101.5531	$101.55	$101.55	$101.60
Purchase #5	$90.77	8.667%	$98.637	$98.64	$98.65	$98.60
Purchase #6	$51.30	8.192%	$55.5025	$55.50	$55.50	$55.50
Purchase #7	$183.67	8.536%	$199.3481	$199.35	$199.35	$199.30
7 purchase totals =	$928.36		$1,023.8188	$1,023.82	$1,023.85	$1,023.80