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	$95.57	6.311%	$101.6014	$101.60	$101.60	$101.60
Purchase #2	$213.36	6.795%	$227.8578	$227.86	$227.85	$227.90
Purchase #3	$67.50	12.706%	$76.0766	$76.08	$76.10	$76.10
Purchase #4	$135.69	11.734%	$151.6119	$151.61	$151.60	$151.60
Purchase #5	$189.40	8.267%	$205.0577	$205.06	$205.05	$205.10
Purchase #6	$168.56	8.838%	$183.4573	$183.46	$183.45	$183.50
Purchase #7	$52.66	12.734%	$59.3657	$59.37	$59.35	$59.40
7 purchase totals =	$922.74		$1,005.0284	$1,005.04	$1,005.00	$1,005.20