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	$195.73	13.704%	$222.5528	$222.55	$222.55	$222.60
Purchase #2	$112.87	6.592%	$120.3104	$120.31	$120.30	$120.30
Purchase #3	$166.64	8.498%	$180.8011	$180.80	$180.80	$180.80
Purchase #4	$19.30	5.126%	$20.2893	$20.29	$20.30	$20.30
Purchase #5	$77.68	5.448%	$81.912	$81.91	$81.90	$81.90
Purchase #6	$68.73	5.467%	$72.4875	$72.49	$72.50	$72.50
Purchase #7	$106.57	9.339%	$116.5226	$116.52	$116.50	$116.50
7 purchase totals =	$747.52		$814.8757	$814.87	$814.85	$814.90