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	$179.68	8.429%	$194.8252	$194.83	$194.85	$194.80
Purchase #2	$29.35	6.120%	$31.1462	$31.15	$31.15	$31.10
Purchase #3	$23.28	5.393%	$24.5355	$24.54	$24.55	$24.50
Purchase #4	$242.64	12.139%	$272.0941	$272.09	$272.10	$272.10
Purchase #5	$150.68	13.721%	$171.3548	$171.35	$171.35	$171.40
Purchase #6	$96.85	3.408%	$100.1506	$100.15	$100.15	$100.20
Purchase #7	$201.42	10.769%	$223.1109	$223.11	$223.10	$223.10
7 purchase totals =	$923.90		$1,017.2173	$1,017.22	$1,017.25	$1,017.20