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	$133.33	3.595%	$138.1232	$138.12	$138.10	$138.10
Purchase #2	$118.94	10.443%	$131.3609	$131.36	$131.35	$131.40
Purchase #3	$212.26	9.835%	$233.1358	$233.14	$233.15	$233.10
Purchase #4	$184.51	13.700%	$209.7879	$209.79	$209.80	$209.80
Purchase #5	$127.74	6.584%	$136.1504	$136.15	$136.15	$136.20
Purchase #6	$116.43	5.874%	$123.2691	$123.27	$123.25	$123.30
Purchase #7	$35.62	13.844%	$40.5512	$40.55	$40.55	$40.60
7 purchase totals =	$928.83		$1,012.3785	$1,012.38	$1,012.35	$1,012.50