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	$204.48	9.784%	$224.4863	$224.49	$224.50	$224.50
Purchase #2	$165.48	10.838%	$183.4147	$183.41	$183.40	$183.40
Purchase #3	$85.40	3.140%	$88.0816	$88.08	$88.10	$88.10
Purchase #4	$89.73	11.119%	$99.7071	$99.71	$99.70	$99.70
Purchase #5	$73.27	8.233%	$79.3023	$79.30	$79.30	$79.30
Purchase #6	$112.88	4.416%	$117.8648	$117.86	$117.85	$117.90
Purchase #7	$90.49	13.834%	$103.0084	$103.01	$103.00	$103.00
7 purchase totals =	$821.73		$895.8652	$895.86	$895.85	$895.90