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	$70.50	3.194%	$72.7518	$72.75	$72.75	$72.80
Purchase #2	$56.72	4.757%	$59.4182	$59.42	$59.40	$59.40
Purchase #3	$217.55	4.279%	$226.859	$226.86	$226.85	$226.90
Purchase #4	$192.59	6.780%	$205.6476	$205.65	$205.65	$205.60
Purchase #5	$32.50	4.665%	$34.0161	$34.02	$34.00	$34.00
Purchase #6	$138.30	11.323%	$153.9597	$153.96	$153.95	$154.00
Purchase #7	$62.55	11.119%	$69.5049	$69.50	$69.50	$69.50
7 purchase totals =	$770.71		$822.1573	$822.16	$822.10	$822.20