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	$57.82	9.833%	$63.5054	$63.51	$63.50	$63.50
Purchase #2	$158.82	12.357%	$178.4454	$178.45	$178.45	$178.40
Purchase #3	$108.47	4.733%	$113.6039	$113.60	$113.60	$113.60
Purchase #4	$235.35	7.836%	$253.792	$253.79	$253.80	$253.80
Purchase #5	$171.34	6.390%	$182.2886	$182.29	$182.30	$182.30
Purchase #6	$78.32	5.866%	$82.9143	$82.91	$82.90	$82.90
Purchase #7	$216.76	3.497%	$224.3401	$224.34	$224.35	$224.30
7 purchase totals =	$1,026.88		$1,098.8897	$1,098.89	$1,098.90	$1,098.80