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	$132.47	9.830%	$145.4918	$145.49	$145.50	$145.50
Purchase #2	$222.77	9.712%	$244.4054	$244.41	$244.40	$244.40
Purchase #3	$106.84	12.736%	$120.4471	$120.45	$120.45	$120.40
Purchase #4	$100.98	12.145%	$113.244	$113.24	$113.25	$113.20
Purchase #5	$103.95	4.351%	$108.4729	$108.47	$108.45	$108.50
Purchase #6	$139.39	3.594%	$144.3997	$144.40	$144.40	$144.40
Purchase #7	$113.36	13.381%	$128.5287	$128.53	$128.55	$128.50
7 purchase totals =	$919.76		$1,004.9896	$1,004.99	$1,005.00	$1,004.90