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	$218.58	3.258%	$225.7013	$225.70	$225.70	$225.70
Purchase #2	$221.90	8.772%	$241.3651	$241.37	$241.35	$241.40
Purchase #3	$102.72	8.527%	$111.4789	$111.48	$111.50	$111.50
Purchase #4	$43.82	3.380%	$45.3011	$45.30	$45.30	$45.30
Purchase #5	$97.35	13.771%	$110.7561	$110.76	$110.75	$110.80
Purchase #6	$151.27	7.390%	$162.4489	$162.45	$162.45	$162.40
Purchase #7	$104.40	7.704%	$112.443	$112.44	$112.45	$112.40
7 purchase totals =	$940.04		$1,009.4944	$1,009.50	$1,009.50	$1,009.50