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	$224.32	7.660%	$241.5029	$241.50	$241.50	$241.50
Purchase #2	$160.89	8.219%	$174.1135	$174.11	$174.10	$174.10
Purchase #3	$72.79	5.231%	$76.5976	$76.60	$76.60	$76.60
Purchase #4	$72.51	3.199%	$74.8296	$74.83	$74.85	$74.80
Purchase #5	$164.87	9.792%	$181.0141	$181.01	$181.00	$181.00
Purchase #6	$89.65	13.145%	$101.4345	$101.43	$101.45	$101.40
Purchase #7	$160.29	5.672%	$169.3816	$169.38	$169.40	$169.40
7 purchase totals =	$945.32		$1,018.8738	$1,018.86	$1,018.90	$1,018.80