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	$206.75	7.587%	$222.4361	$222.44	$222.45	$222.40
Purchase #2	$175.30	10.366%	$193.4716	$193.47	$193.45	$193.50
Purchase #3	$75.40	6.331%	$80.1736	$80.17	$80.15	$80.20
Purchase #4	$67.33	7.152%	$72.1454	$72.15	$72.15	$72.10
Purchase #5	$100.89	13.444%	$114.4537	$114.45	$114.45	$114.50
Purchase #6	$121.98	8.383%	$132.2056	$132.21	$132.20	$132.20
Purchase #7	$203.78	7.710%	$219.4914	$219.49	$219.50	$219.50
7 purchase totals =	$951.43		$1,034.3774	$1,034.38	$1,034.35	$1,034.40