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	$39.68	4.493%	$41.4628	$41.46	$41.45	$41.50
Purchase #2	$226.64	12.373%	$254.6822	$254.68	$254.70	$254.70
Purchase #3	$100.59	10.448%	$111.0996	$111.10	$111.10	$111.10
Purchase #4	$178.58	6.466%	$190.127	$190.13	$190.15	$190.10
Purchase #5	$147.45	8.579%	$160.0997	$160.10	$160.10	$160.10
Purchase #6	$220.26	6.650%	$234.9073	$234.91	$234.90	$234.90
Purchase #7	$43.85	9.697%	$48.1021	$48.10	$48.10	$48.10
7 purchase totals =	$957.05		$1,040.4807	$1,040.48	$1,040.50	$1,040.50