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	$189.26	3.600%	$196.0734	$196.07	$196.05	$196.10
Purchase #2	$52.83	13.152%	$59.7782	$59.78	$59.80	$59.80
Purchase #3	$160.39	7.756%	$172.8298	$172.83	$172.85	$172.80
Purchase #4	$219.42	10.287%	$241.9917	$241.99	$242.00	$242.00
Purchase #5	$28.36	3.279%	$29.2899	$29.29	$29.30	$29.30
Purchase #6	$181.92	13.854%	$207.1232	$207.12	$207.10	$207.10
Purchase #7	$46.69	8.113%	$50.478	$50.48	$50.50	$50.50
7 purchase totals =	$878.87		$957.5642	$957.56	$957.60	$957.60