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	$222.84	4.672%	$233.2511	$233.25	$233.25	$233.30
Purchase #2	$142.46	9.798%	$156.4182	$156.42	$156.40	$156.40
Purchase #3	$87.61	5.104%	$92.0816	$92.08	$92.10	$92.10
Purchase #4	$100.93	7.387%	$108.3857	$108.39	$108.40	$108.40
Purchase #5	$51.98	10.704%	$57.5439	$57.54	$57.55	$57.50
Purchase #6	$162.32	13.226%	$183.7884	$183.79	$183.80	$183.80
Purchase #7	$169.45	13.167%	$191.7615	$191.76	$191.75	$191.80
7 purchase totals =	$937.59		$1,023.2304	$1,023.23	$1,023.25	$1,023.30