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	$83.48	10.820%	$92.5125	$92.51	$92.50	$92.50
Purchase #2	$29.88	13.783%	$33.9984	$34.00	$34.00	$34.00
Purchase #3	$104.29	8.407%	$113.0577	$113.06	$113.05	$113.10
Purchase #4	$92.30	11.676%	$103.0769	$103.08	$103.10	$103.10
Purchase #5	$186.59	10.224%	$205.667	$205.67	$205.65	$205.70
Purchase #6	$110.83	13.786%	$126.109	$126.11	$126.10	$126.10
Purchase #7	$238.80	10.605%	$264.1247	$264.12	$264.10	$264.10
7 purchase totals =	$846.17		$938.5462	$938.55	$938.50	$938.60