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	$171.30	7.761%	$184.5946	$184.59	$184.60	$184.60
Purchase #2	$37.54	3.833%	$38.9789	$38.98	$39.00	$39.00
Purchase #3	$46.56	9.163%	$50.8263	$50.83	$50.85	$50.80
Purchase #4	$216.42	6.805%	$231.1474	$231.15	$231.15	$231.10
Purchase #5	$142.62	5.328%	$150.2188	$150.22	$150.20	$150.20
Purchase #6	$123.85	3.695%	$128.4263	$128.43	$128.45	$128.40
Purchase #7	$231.49	5.788%	$244.8886	$244.89	$244.90	$244.90
7 purchase totals =	$969.78		$1,029.0809	$1,029.09	$1,029.15	$1,029.00