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	$53.68	11.264%	$59.7265	$59.73	$59.75	$59.70
Purchase #2	$100.32	11.246%	$111.602	$111.60	$111.60	$111.60
Purchase #3	$236.64	9.715%	$259.6296	$259.63	$259.65	$259.60
Purchase #4	$54.40	9.643%	$59.6458	$59.65	$59.65	$59.60
Purchase #5	$91.63	12.503%	$103.0865	$103.09	$103.10	$103.10
Purchase #6	$21.79	12.849%	$24.5898	$24.59	$24.60	$24.60
Purchase #7	$110.30	9.343%	$120.6053	$120.61	$120.60	$120.60
7 purchase totals =	$668.76		$738.8855	$738.90	$738.95	$738.80