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	$236.43	11.345%	$263.253	$263.25	$263.25	$263.30
Purchase #2	$165.38	10.327%	$182.4588	$182.46	$182.45	$182.50
Purchase #3	$102.81	6.804%	$109.8052	$109.81	$109.80	$109.80
Purchase #4	$216.43	9.696%	$237.4151	$237.42	$237.40	$237.40
Purchase #5	$92.90	7.383%	$99.7588	$99.76	$99.75	$99.80
Purchase #6	$246.89	4.110%	$257.0372	$257.04	$257.05	$257.00
Purchase #7	$103.43	5.619%	$109.2417	$109.24	$109.25	$109.20
7 purchase totals =	$1,164.27		$1,258.9698	$1,258.98	$1,258.95	$1,259.00