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	$134.99	3.459%	$139.6593	$139.66	$139.65	$139.70
Purchase #2	$98.62	13.693%	$112.124	$112.12	$112.10	$112.10
Purchase #3	$9.31	8.565%	$10.1074	$10.11	$10.10	$10.10
Purchase #4	$66.52	3.104%	$68.5848	$68.58	$68.60	$68.60
Purchase #5	$212.90	4.298%	$222.0504	$222.05	$222.05	$222.10
Purchase #6	$219.64	6.116%	$233.0732	$233.07	$233.05	$233.10
Purchase #7	$196.92	11.683%	$219.9262	$219.93	$219.95	$219.90
7 purchase totals =	$938.90		$1,005.5253	$1,005.52	$1,005.50	$1,005.60