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	$134.34	6.537%	$143.1218	$143.12	$143.10	$143.10
Purchase #2	$149.41	6.347%	$158.8931	$158.89	$158.90	$158.90
Purchase #3	$119.96	4.728%	$125.6317	$125.63	$125.65	$125.60
Purchase #4	$230.53	4.807%	$241.6116	$241.61	$241.60	$241.60
Purchase #5	$202.69	13.225%	$229.4958	$229.50	$229.50	$229.50
Purchase #6	$202.63	5.850%	$214.4839	$214.48	$214.50	$214.50
Purchase #7	$59.29	13.551%	$67.3244	$67.32	$67.30	$67.30
7 purchase totals =	$1,098.85		$1,180.5623	$1,180.55	$1,180.55	$1,180.50