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	$244.66	9.612%	$268.1767	$268.18	$268.20	$268.20
Purchase #2	$132.61	11.874%	$148.3561	$148.36	$148.35	$148.40
Purchase #3	$54.27	5.863%	$57.4519	$57.45	$57.45	$57.50
Purchase #4	$147.57	3.402%	$152.5903	$152.59	$152.60	$152.60
Purchase #5	$241.75	11.791%	$270.2547	$270.25	$270.25	$270.30
Purchase #6	$201.87	8.656%	$219.3439	$219.34	$219.35	$219.30
Purchase #7	$27.25	5.161%	$28.6564	$28.66	$28.65	$28.70
7 purchase totals =	$1,049.98		$1,144.8300	$1,144.83	$1,144.85	$1,145.00