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	$133.72	10.371%	$147.5881	$147.59	$147.60	$147.60
Purchase #2	$22.81	4.853%	$23.917	$23.92	$23.90	$23.90
Purchase #3	$176.83	5.258%	$186.1277	$186.13	$186.15	$186.10
Purchase #4	$235.47	6.402%	$250.5448	$250.54	$250.55	$250.50
Purchase #5	$130.53	8.246%	$141.2935	$141.29	$141.30	$141.30
Purchase #6	$19.51	10.453%	$21.5494	$21.55	$21.55	$21.50
Purchase #7	$118.85	10.261%	$131.0452	$131.05	$131.05	$131.00
7 purchase totals =	$837.72		$902.0657	$902.07	$902.10	$901.90