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	$169.49	8.541%	$183.9661	$183.97	$183.95	$184.00
Purchase #2	$38.35	10.720%	$42.4611	$42.46	$42.45	$42.50
Purchase #3	$84.98	11.469%	$94.7264	$94.73	$94.75	$94.70
Purchase #4	$158.50	5.535%	$167.273	$167.27	$167.25	$167.30
Purchase #5	$152.48	10.442%	$168.402	$168.40	$168.40	$168.40
Purchase #6	$145.99	6.558%	$155.564	$155.56	$155.55	$155.60
Purchase #7	$113.77	12.611%	$128.1175	$128.12	$128.10	$128.10
7 purchase totals =	$863.56		$940.5101	$940.51	$940.45	$940.60