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	$59.83	8.115%	$64.6852	$64.69	$64.70	$64.70
Purchase #2	$120.87	10.712%	$133.8176	$133.82	$133.80	$133.80
Purchase #3	$18.26	6.728%	$19.4885	$19.49	$19.50	$19.50
Purchase #4	$54.56	8.168%	$59.0165	$59.02	$59.00	$59.00
Purchase #5	$134.86	3.239%	$139.2281	$139.23	$139.25	$139.20
Purchase #6	$144.85	13.307%	$164.1252	$164.13	$164.15	$164.10
Purchase #7	$182.92	12.389%	$205.582	$205.58	$205.60	$205.60
7 purchase totals =	$716.15		$785.9431	$785.96	$786.00	$785.90