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	$148.67	12.731%	$167.5972	$167.60	$167.60	$167.60
Purchase #2	$47.82	9.803%	$52.5078	$52.51	$52.50	$52.50
Purchase #3	$103.58	7.581%	$111.4324	$111.43	$111.45	$111.40
Purchase #4	$188.42	13.804%	$214.4295	$214.43	$214.45	$214.40
Purchase #5	$30.57	11.847%	$34.1916	$34.19	$34.20	$34.20
Purchase #6	$171.59	11.392%	$191.1375	$191.14	$191.15	$191.10
Purchase #7	$92.61	5.659%	$97.8508	$97.85	$97.85	$97.90
7 purchase totals =	$783.26		$869.1468	$869.15	$869.20	$869.10