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	$144.50	8.190%	$156.3346	$156.33	$156.35	$156.30
Purchase #2	$193.59	6.229%	$205.6487	$205.65	$205.65	$205.60
Purchase #3	$225.85	12.186%	$253.3721	$253.37	$253.35	$253.40
Purchase #4	$200.73	7.403%	$215.59	$215.59	$215.60	$215.60
Purchase #5	$49.47	13.735%	$56.2647	$56.26	$56.25	$56.30
Purchase #6	$7.51	11.859%	$8.4006	$8.40	$8.40	$8.40
Purchase #7	$41.88	8.403%	$45.3992	$45.40	$45.40	$45.40
7 purchase totals =	$863.53		$941.0099	$941.00	$941.00	$941.00