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	$171.31	7.691%	$184.4855	$184.49	$184.50	$184.50
Purchase #2	$230.56	7.249%	$247.2733	$247.27	$247.25	$247.30
Purchase #3	$95.66	4.627%	$100.0862	$100.09	$100.10	$100.10
Purchase #4	$150.48	3.574%	$155.8582	$155.86	$155.85	$155.90
Purchase #5	$12.46	3.517%	$12.8982	$12.90	$12.90	$12.90
Purchase #6	$97.85	12.189%	$109.7769	$109.78	$109.80	$109.80
Purchase #7	$90.37	10.228%	$99.613	$99.61	$99.60	$99.60
7 purchase totals =	$848.69		$909.9913	$910.00	$910.00	$910.10