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	$104.69	7.869%	$112.9281	$112.93	$112.95	$112.90
Purchase #2	$92.65	8.488%	$100.5141	$100.51	$100.50	$100.50
Purchase #3	$177.51	9.467%	$194.3149	$194.31	$194.30	$194.30
Purchase #4	$45.57	4.587%	$47.6603	$47.66	$47.65	$47.70
Purchase #5	$123.87	12.233%	$139.023	$139.02	$139.00	$139.00
Purchase #6	$92.94	7.779%	$100.1698	$100.17	$100.15	$100.20
Purchase #7	$177.82	4.790%	$186.3376	$186.34	$186.35	$186.30
7 purchase totals =	$815.05		$880.9478	$880.94	$880.90	$880.90