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	$86.60	9.180%	$94.5499	$94.55	$94.55	$94.50
Purchase #2	$59.53	10.646%	$65.8676	$65.87	$65.85	$65.90
Purchase #3	$77.59	4.107%	$80.7766	$80.78	$80.80	$80.80
Purchase #4	$160.72	4.411%	$167.8094	$167.81	$167.80	$167.80
Purchase #5	$179.65	6.639%	$191.577	$191.58	$191.60	$191.60
Purchase #6	$115.88	13.133%	$131.0985	$131.10	$131.10	$131.10
Purchase #7	$186.74	6.514%	$198.9042	$198.90	$198.90	$198.90
7 purchase totals =	$866.71		$930.5832	$930.59	$930.60	$930.60