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	$205.27	13.708%	$233.4084	$233.41	$233.40	$233.40
Purchase #2	$29.46	13.564%	$33.456	$33.46	$33.45	$33.50
Purchase #3	$68.80	13.768%	$78.2724	$78.27	$78.25	$78.30
Purchase #4	$107.25	9.293%	$117.2167	$117.22	$117.20	$117.20
Purchase #5	$224.48	6.396%	$238.8377	$238.84	$238.85	$238.80
Purchase #6	$230.31	10.240%	$253.8937	$253.89	$253.90	$253.90
Purchase #7	$93.76	8.605%	$101.828	$101.83	$101.85	$101.80
7 purchase totals =	$959.33		$1,056.9129	$1,056.92	$1,056.90	$1,056.90