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	$219.33	12.422%	$246.5752	$246.58	$246.60	$246.60
Purchase #2	$207.25	12.701%	$233.5728	$233.57	$233.55	$233.60
Purchase #3	$93.73	8.311%	$101.5199	$101.52	$101.50	$101.50
Purchase #4	$171.89	8.799%	$187.0146	$187.01	$187.00	$187.00
Purchase #5	$119.61	3.555%	$123.8621	$123.86	$123.85	$123.90
Purchase #6	$107.27	10.284%	$118.3016	$118.30	$118.30	$118.30
Purchase #7	$231.75	10.652%	$256.436	$256.44	$256.45	$256.40
7 purchase totals =	$1,150.83		$1,267.2822	$1,267.28	$1,267.25	$1,267.30