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	$99.90	10.605%	$110.4944	$110.49	$110.50	$110.50
Purchase #2	$107.28	11.414%	$119.5249	$119.52	$119.50	$119.50
Purchase #3	$184.33	5.568%	$194.5935	$194.59	$194.60	$194.60
Purchase #4	$118.40	4.462%	$123.683	$123.68	$123.70	$123.70
Purchase #5	$242.98	3.244%	$250.8623	$250.86	$250.85	$250.90
Purchase #6	$111.38	3.612%	$115.403	$115.40	$115.40	$115.40
Purchase #7	$145.56	5.375%	$153.3839	$153.38	$153.40	$153.40
7 purchase totals =	$1,009.83		$1,067.9450	$1,067.92	$1,067.95	$1,068.00