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	$78.89	4.716%	$82.6105	$82.61	$82.60	$82.60
Purchase #2	$29.61	12.489%	$33.308	$33.31	$33.30	$33.30
Purchase #3	$198.59	9.398%	$217.2535	$217.25	$217.25	$217.30
Purchase #4	$187.92	12.293%	$211.021	$211.02	$211.00	$211.00
Purchase #5	$19.32	5.493%	$20.3812	$20.38	$20.40	$20.40
Purchase #6	$182.32	10.472%	$201.4126	$201.41	$201.40	$201.40
Purchase #7	$173.72	11.844%	$194.2954	$194.30	$194.30	$194.30
7 purchase totals =	$870.37		$960.2822	$960.28	$960.25	$960.30