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	$168.68	6.289%	$179.2883	$179.29	$179.30	$179.30
Purchase #2	$167.59	8.524%	$181.8754	$181.88	$181.90	$181.90
Purchase #3	$68.49	4.116%	$71.309	$71.31	$71.30	$71.30
Purchase #4	$58.59	12.157%	$65.7128	$65.71	$65.70	$65.70
Purchase #5	$43.80	8.215%	$47.3982	$47.40	$47.40	$47.40
Purchase #6	$24.96	13.382%	$28.3001	$28.30	$28.30	$28.30
Purchase #7	$230.96	4.606%	$241.598	$241.60	$241.60	$241.60
7 purchase totals =	$763.07		$815.4818	$815.49	$815.50	$815.50