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	$88.90	5.540%	$93.8251	$93.83	$93.85	$93.80
Purchase #2	$60.75	12.577%	$68.3905	$68.39	$68.40	$68.40
Purchase #3	$102.57	11.707%	$114.5779	$114.58	$114.60	$114.60
Purchase #4	$137.85	7.374%	$148.0151	$148.02	$148.00	$148.00
Purchase #5	$70.87	11.348%	$78.9123	$78.91	$78.90	$78.90
Purchase #6	$132.50	5.344%	$139.5808	$139.58	$139.60	$139.60
Purchase #7	$70.94	11.198%	$78.8839	$78.88	$78.90	$78.90
7 purchase totals =	$664.38		$722.1856	$722.19	$722.25	$722.20