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	$248.27	4.260%	$258.8463	$258.85	$258.85	$258.80
Purchase #2	$29.82	12.524%	$33.5547	$33.55	$33.55	$33.60
Purchase #3	$146.60	3.846%	$152.2382	$152.24	$152.25	$152.20
Purchase #4	$131.86	5.716%	$139.3971	$139.40	$139.40	$139.40
Purchase #5	$7.55	4.127%	$7.8616	$7.86	$7.85	$7.90
Purchase #6	$108.66	10.706%	$120.2931	$120.29	$120.30	$120.30
Purchase #7	$47.47	12.157%	$53.2409	$53.24	$53.25	$53.20
7 purchase totals =	$720.23		$765.4319	$765.43	$765.45	$765.40