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	$103.39	7.450%	$111.0926	$111.09	$111.10	$111.10
Purchase #2	$244.32	8.573%	$265.2656	$265.27	$265.25	$265.30
Purchase #3	$158.83	9.302%	$173.6044	$173.60	$173.60	$173.60
Purchase #4	$214.49	12.543%	$241.3935	$241.39	$241.40	$241.40
Purchase #5	$31.82	3.456%	$32.9197	$32.92	$32.90	$32.90
Purchase #6	$170.50	6.171%	$181.0216	$181.02	$181.00	$181.00
Purchase #7	$33.34	10.839%	$36.9537	$36.95	$36.95	$37.00
7 purchase totals =	$956.69		$1,042.2511	$1,042.24	$1,042.20	$1,042.30