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	$68.27	12.215%	$76.6092	$76.61	$76.60	$76.60
Purchase #2	$133.78	4.870%	$140.2951	$140.30	$140.30	$140.30
Purchase #3	$66.70	6.227%	$70.8534	$70.85	$70.85	$70.90
Purchase #4	$186.90	5.182%	$196.5852	$196.59	$196.60	$196.60
Purchase #5	$179.56	9.151%	$195.9915	$195.99	$196.00	$196.00
Purchase #6	$107.69	8.687%	$117.045	$117.05	$117.05	$117.00
Purchase #7	$233.38	4.307%	$243.4317	$243.43	$243.45	$243.40
7 purchase totals =	$976.28		$1,040.8111	$1,040.82	$1,040.85	$1,040.80