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	$211.36	10.839%	$234.2693	$234.27	$234.25	$234.30
Purchase #2	$197.58	4.294%	$206.0641	$206.06	$206.05	$206.10
Purchase #3	$82.33	12.354%	$92.501	$92.50	$92.50	$92.50
Purchase #4	$177.51	3.836%	$184.3193	$184.32	$184.30	$184.30
Purchase #5	$211.27	3.463%	$218.5863	$218.59	$218.60	$218.60
Purchase #6	$47.82	6.816%	$51.0794	$51.08	$51.10	$51.10
Purchase #7	$132.36	9.192%	$144.5265	$144.53	$144.55	$144.50
7 purchase totals =	$1,060.23		$1,131.3459	$1,131.35	$1,131.35	$1,131.40