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	$117.47	3.469%	$121.545	$121.55	$121.55	$121.50
Purchase #2	$68.42	6.428%	$72.818	$72.82	$72.80	$72.80
Purchase #3	$196.39	5.579%	$207.3466	$207.35	$207.35	$207.30
Purchase #4	$38.86	12.404%	$43.6802	$43.68	$43.70	$43.70
Purchase #5	$192.92	11.482%	$215.0711	$215.07	$215.05	$215.10
Purchase #6	$215.59	8.487%	$233.8871	$233.89	$233.90	$233.90
Purchase #7	$165.25	8.404%	$179.1376	$179.14	$179.15	$179.10
7 purchase totals =	$994.90		$1,073.4856	$1,073.50	$1,073.50	$1,073.40