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	$97.33	6.313%	$103.4744	$103.47	$103.45	$103.50
Purchase #2	$121.52	13.109%	$137.4501	$137.45	$137.45	$137.50
Purchase #3	$166.61	11.302%	$185.4403	$185.44	$185.45	$185.40
Purchase #4	$62.85	13.280%	$71.1965	$71.20	$71.20	$71.20
Purchase #5	$138.72	9.126%	$151.3796	$151.38	$151.40	$151.40
Purchase #6	$224.43	8.538%	$243.5918	$243.59	$243.60	$243.60
Purchase #7	$156.81	6.789%	$167.4558	$167.46	$167.45	$167.50
7 purchase totals =	$968.27		$1,059.9885	$1,059.99	$1,060.00	$1,060.10