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	$44.61	9.634%	$48.9077	$48.91	$48.90	$48.90
Purchase #2	$39.39	8.849%	$42.8756	$42.88	$42.90	$42.90
Purchase #3	$86.92	5.611%	$91.7971	$91.80	$91.80	$91.80
Purchase #4	$236.42	5.184%	$248.676	$248.68	$248.70	$248.70
Purchase #5	$16.61	4.475%	$17.3533	$17.35	$17.35	$17.40
Purchase #6	$54.35	3.181%	$56.0789	$56.08	$56.10	$56.10
Purchase #7	$54.51	9.267%	$59.5614	$59.56	$59.55	$59.60
7 purchase totals =	$532.81		$565.2500	$565.26	$565.30	$565.40