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	$66.29	9.215%	$72.3986	$72.40	$72.40	$72.40
Purchase #2	$108.97	12.759%	$122.8735	$122.87	$122.85	$122.90
Purchase #3	$38.69	13.130%	$43.77	$43.77	$43.75	$43.80
Purchase #4	$241.52	11.587%	$269.5049	$269.50	$269.50	$269.50
Purchase #5	$32.29	10.102%	$35.5519	$35.55	$35.55	$35.60
Purchase #6	$102.92	9.213%	$112.402	$112.40	$112.40	$112.40
Purchase #7	$73.27	11.853%	$81.9547	$81.95	$81.95	$82.00
7 purchase totals =	$663.95		$738.4556	$738.44	$738.40	$738.60