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	$170.78	4.391%	$178.2789	$178.28	$178.30	$178.30
Purchase #2	$167.71	8.146%	$181.3717	$181.37	$181.35	$181.40
Purchase #3	$90.88	5.492%	$95.8711	$95.87	$95.85	$95.90
Purchase #4	$205.64	10.407%	$227.041	$227.04	$227.05	$227.00
Purchase #5	$84.27	10.857%	$93.4192	$93.42	$93.40	$93.40
Purchase #6	$182.58	7.353%	$196.0051	$196.01	$196.00	$196.00
Purchase #7	$161.66	12.779%	$182.3185	$182.32	$182.30	$182.30
7 purchase totals =	$1,063.52		$1,154.3055	$1,154.31	$1,154.25	$1,154.30