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	$167.49	11.822%	$187.2907	$187.29	$187.30	$187.30
Purchase #2	$165.30	4.228%	$172.2889	$172.29	$172.30	$172.30
Purchase #3	$164.51	10.343%	$181.5253	$181.53	$181.55	$181.50
Purchase #4	$76.78	4.794%	$80.4608	$80.46	$80.45	$80.50
Purchase #5	$113.96	5.834%	$120.6084	$120.61	$120.60	$120.60
Purchase #6	$247.47	5.189%	$260.3112	$260.31	$260.30	$260.30
Purchase #7	$143.95	6.664%	$153.5428	$153.54	$153.55	$153.50
7 purchase totals =	$1,079.46		$1,156.0281	$1,156.03	$1,156.05	$1,156.00