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	$215.60	8.333%	$233.5659	$233.57	$233.55	$233.60
Purchase #2	$160.90	7.278%	$172.6103	$172.61	$172.60	$172.60
Purchase #3	$131.72	3.299%	$136.0654	$136.07	$136.05	$136.10
Purchase #4	$171.87	11.478%	$191.5972	$191.60	$191.60	$191.60
Purchase #5	$132.91	5.649%	$140.4181	$140.42	$140.40	$140.40
Purchase #6	$10.69	6.358%	$11.3697	$11.37	$11.35	$11.40
Purchase #7	$82.87	11.871%	$92.7075	$92.71	$92.70	$92.70
7 purchase totals =	$906.56		$978.3341	$978.35	$978.25	$978.40