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	$232.79	12.626%	$262.1821	$262.18	$262.20	$262.20
Purchase #2	$51.78	4.564%	$54.1432	$54.14	$54.15	$54.10
Purchase #3	$147.47	11.522%	$164.4615	$164.46	$164.45	$164.50
Purchase #4	$20.63	5.833%	$21.8333	$21.83	$21.85	$21.80
Purchase #5	$166.26	8.650%	$180.6415	$180.64	$180.65	$180.60
Purchase #6	$95.63	7.385%	$102.6923	$102.69	$102.70	$102.70
Purchase #7	$242.62	4.522%	$253.5913	$253.59	$253.60	$253.60
7 purchase totals =	$957.18		$1,039.5452	$1,039.53	$1,039.60	$1,039.50