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	$41.28	12.196%	$46.3145	$46.31	$46.30	$46.30
Purchase #2	$214.83	5.148%	$225.8894	$225.89	$225.90	$225.90
Purchase #3	$227.71	9.136%	$248.5136	$248.51	$248.50	$248.50
Purchase #4	$250.96	12.397%	$282.0715	$282.07	$282.05	$282.10
Purchase #5	$173.51	7.243%	$186.0773	$186.08	$186.10	$186.10
Purchase #6	$80.43	3.474%	$83.2241	$83.22	$83.20	$83.20
Purchase #7	$37.96	5.874%	$40.1898	$40.19	$40.20	$40.20
7 purchase totals =	$1,026.68		$1,112.2802	$1,112.27	$1,112.25	$1,112.30