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	$171.86	5.589%	$181.4653	$181.47	$181.45	$181.50
Purchase #2	$213.58	3.744%	$221.5764	$221.58	$221.60	$221.60
Purchase #3	$152.90	4.516%	$159.805	$159.81	$159.80	$159.80
Purchase #4	$185.45	8.143%	$200.5512	$200.55	$200.55	$200.60
Purchase #5	$113.68	8.489%	$123.3303	$123.33	$123.35	$123.30
Purchase #6	$221.33	5.380%	$233.2376	$233.24	$233.25	$233.20
Purchase #7	$58.40	7.724%	$62.9108	$62.91	$62.90	$62.90
7 purchase totals =	$1,117.20		$1,182.8766	$1,182.89	$1,182.90	$1,182.90