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	$124.83	13.162%	$141.2601	$141.26	$141.25	$141.30
Purchase #2	$89.42	3.168%	$92.2528	$92.25	$92.25	$92.30
Purchase #3	$130.96	6.511%	$139.4868	$139.49	$139.50	$139.50
Purchase #4	$168.75	5.441%	$177.9317	$177.93	$177.95	$177.90
Purchase #5	$133.61	8.693%	$145.2247	$145.22	$145.20	$145.20
Purchase #6	$178.62	9.776%	$196.0819	$196.08	$196.10	$196.10
Purchase #7	$130.94	11.440%	$145.9195	$145.92	$145.90	$145.90
7 purchase totals =	$957.13		$1,038.1575	$1,038.15	$1,038.15	$1,038.20