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	$113.32	4.617%	$118.552	$118.55	$118.55	$118.60
Purchase #2	$179.59	9.235%	$196.1751	$196.18	$196.20	$196.20
Purchase #3	$176.38	13.318%	$199.8703	$199.87	$199.85	$199.90
Purchase #4	$44.67	3.582%	$46.2701	$46.27	$46.25	$46.30
Purchase #5	$188.91	9.858%	$207.5327	$207.53	$207.55	$207.50
Purchase #6	$129.57	7.788%	$139.6609	$139.66	$139.65	$139.70
Purchase #7	$110.88	11.575%	$123.7144	$123.71	$123.70	$123.70
7 purchase totals =	$943.32		$1,031.7755	$1,031.77	$1,031.75	$1,031.90