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	$50.84	7.308%	$54.5554	$54.56	$54.55	$54.60
Purchase #2	$77.78	7.262%	$83.4284	$83.43	$83.45	$83.40
Purchase #3	$144.98	7.839%	$156.345	$156.35	$156.35	$156.30
Purchase #4	$155.25	5.287%	$163.4581	$163.46	$163.45	$163.50
Purchase #5	$58.95	7.123%	$63.149	$63.15	$63.15	$63.10
Purchase #6	$249.44	3.745%	$258.7815	$258.78	$258.80	$258.80
Purchase #7	$128.48	13.153%	$145.379	$145.38	$145.40	$145.40
7 purchase totals =	$865.72		$925.0964	$925.11	$925.15	$925.10